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CHAPTER XIV THE HEAD AND NECK[edit]
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BACK OF THE SCALP AND NECK.
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andmarks. —The external occipital protuberance can, as a rule, be
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out readily enough in the male, and the superior nuchal line,
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ill developed, may be felt extending outwards from it. The oid process of the temporal bone can be distinguished without ulty behind the auricle. The occipital artery, with the greater iital nerve on its inner side, lies about inches to the outer side e external occipital protuberance. The occipital lymphatic gland, [ands, may be felt, when enlarged, over the upper part of the izius or semispinalis capitis muscle. The spine of the seventh cal vertebra, or vertebra prominens, can easily be felt, and that le sixth may also be made out. Extending from the external )ital protuberance to the seventh cervical spine there is an elonI depression, called the nuchal furrow, which indicates the position tie ligamentum nuchse. It is possible to feel the strong bifid 3 of the axis by sinking the finger deeply into the upper part of luchal furrow near the occipital bone, but the spines of the third, Hi, and fifth cervical vertebrae lie too deeply for detection. Lymic glands may be felt, when enlarged, along the posterior border le sterno-mastoid muscle.
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Jack and Side of the Neck—Fasciae. —The superhcial fascia presents ing worthy of note. The deep fascia closely invests the cervical ion of the trapezius, and is then prolonged over the posterior lgle of the neck to the posterior border of the sterno-mastoid, re it divides to ensheathe that muscle. It will be described in lection with the deep cervical fascia.
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Jutaneous Nerves. —The nerves of this region are as follows: the )Ccipital; the greater occipital; the third occipital; the medial iches of the posterior primary rami of the third, fourth, and fifth ical spinal nerves; the lesser occipital; the great auricular; the rior cutaneous nerve of neck; and the descending superficial iches of the cervical plexus—namely, the supraclavicular nerves Fig. 687).
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Die suboccipital nerve is the posterior primary ramus of the first ical nerve; it only occasionally supplies the skin on the outer of the greater occipital area.
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Fhe greater occipital nerve is the medial branch of the posterior lary ramus of the second cervical nerve. It pierces the upper
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A MANUAL OF ANATOMY
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part of the semispinalis capitis muscle, and sometimes the trape2 about -J inch from the middle line. It then runs upwards, with inclination outwards, and accompanies the occipital artery to the era integument, lying on the inner side of that vessel. Its branches long, and have an extensive distribution, reaching as far as the vei of the skull. Laterally it communicates with the small occif nerve, and medially with the third occipital.
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The third occipital nerve is a small offset from the me branch of the posterior primary ramus of the third cervical ne Having pierced the trapezius, it ascends medial to the gre; occipital nerve, with which it communicates, and has a lim distribution to the occipital integument inside that nerve.
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The medial bran< of the posterior prin rami of the third, fou and fifth cervical ne; appear through trapezius close to middle line, and t outwards to supply skin of the back of neck, that of the tl furnishing, as j stated, the third c pital nerve.
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The lesser occij nerve is one of the cending superfw branches of the cerv plexus, and arises fi the anterior prim ramus of the sec cervical nerve, so times receiving a bra from that of the third. It appears at the posterior border of the stei mastoid muscle, and ascends along that border to the occipital reg Here it divides into mastoid and occipital branches, which supply skin of the mastoid, outer part of the occipital, and adjacent porl of the parietal regions. It furnishes an auricular branch to the 5 of the upper part of the inner surface of the auricle, and it commi cates with the greater occipital, the posterior branch of the gi auricular, and the posterior auricular branch of the facial, lesser occipital nerve is sometimes double, and in these cases one port of it usually pierces the anterior border of the trapezius.
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The great auricular nerve, like the lesser occipital, is one of ascending superficial branches of the cervical plexus, and arises two roots from the anterior primary rami of the second and tl cervical nerves. It turns round the posterior border of the stei
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Occ. Front.
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G. Occ. N. Third Occ. N. Less. Occ. N.
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Fig. 687.—To show the Nerves and Vessels on the Back of Scalp and Neck.
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THE HEAD AND-NECK
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istoid immediately below the lesser occipital nerve, and passes wards and forwards upon that muscle towards the lobule of the ricle, on approaching which it divides into anterior and posterior anches. The posterior branch is distributed to the skin over the istoid region, the skin of the inner surface of the auricle, and sends e or two twigs through the cartilage of the auricle to the skin covery the lower part of the outer surface; and the anterior branch is dis
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Auricularis Anterior
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Auricularis Superior
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Auricularis Posterior
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Occipital Belly of Occipito-frontalis
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Greater Occipital Nerve Semispinalis Capitis Lesser Occipital Nerve
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Splenius Capitis
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Levator Scapulae
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Great Auricular Nerve
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Accessory Nerv e anches from Third and Fourth Cervical Nerves to Trapezius Scalenus Medius
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Lateral Supraclavicular Nerve
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Trapezius
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' Frontal Belly of Occipitofrontalis
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Orbicularis Oculi
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Levator Labii Superioris Alaeque Nasi
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Levator Labii Superioris - Zygomaticus Minor Zygomaticus Major
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Masseter Orbicularis Oris Depressor Labii Inferioris _ Depressor Anguli Oris Mentalis
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Anterior Belly of Digastric Stemo-hyoid
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Superior Belly of Omo-hyoid Sterno-mastoid
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Anterior Cutaneous Nerve of the Neck
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— Medial Supraclavicular Nerve
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— Intermediate Supraclavicular Nerve
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Scalenus Anterior
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»
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Inferior Belly of Omo-hyoid Subclavian Artery (third part)
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Fig. 688.—The Right Side of the Head and Neck. The platysma has been removed, and the nerves are shown.
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ibuted to the skin over the parotid gland and angle of the jaw. The )sterior branch communicates with the lesser occipital and posterior lricular nerves, and the anterior branch communicates in the parotid and with the facial nerve.
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The anterior cutaneous nerve of the neck (transverse cervical irve), like the lesser occipital and great auricular, is a superficial 'anch of the cervical plexus, and arises by two roots from the anterioi
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ii 4 4
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A MANUAL OF ANATOMY
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primary rami of the second and third or third and fourth cervic nerves. It appears at the posterior border of the sterno-mastc close below the great auricular, and turns over that muscle deep the external jugular vein to reach the front of the neck, where it w be afterwards described.
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The supraclavicular nerves from the cervical plexus appear at t posterior border of the sterno-mastoid below the accessory, usua] as a single trunk which arises by two roots from the anterior prima rami of the third and fourth cervical nerves or from the fourth alor This trunk, as it descends, divides into three branches—name] medial, intermediate, and lateral —which pass downwards over t clavicle, and will be afterwards referred to.
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Deeper Structures.
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Ligamentum Nuchse. —This is a strong fibrous band which occupi the median line of the neck. Its superficial fibres are attached superior to the external occipital protuberance, and interiorly to the spi of the seventh cervical vertebra. Its deep fibres are attached the external occipital crest, and to the spines of cervical vertebr from the second to the sixth inclusive. They also extend into t interspinous intervals between the interspinales muscles, where th represent interspinous ligaments.
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Muscles—Cervical Portion of the Trapezius — Origin. —fi) T inner third of the superior nuchal line of the occipital bone, and t] external occipital protuberance; and (2) the ligamentum nuchse.
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Insertion. —(1) The posterior border of the outer third of ti clavicle; and (2) the inner border of the acromion process of t] scapula.
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Nerve-supply. — (1) The accessory nerve (spinal root); ai (2) branches from the cervical plexus, which are derived from t] anterior primary rami of the third and fourth cervical nerves. T] nerves enter the deep surface of the muscle after passing benea its anterior border a little above the clavicle, and they here for a plexiform communication with each other.
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Blood-supply .—The superficial branch (superficial cervical arter of the transverse cervical artery ramifies on and gives branches the deep surface of the muscle.
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The fibres are directed downwards, forwards, and outwards.
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This part of the muscle lies on the semispinalis capitis just belo the occiput, and below this on the splenius and levator scapuke; tl superficial branch of the transverse cervical artery and superfici branch of the ramus descendens (arteria princeps cervicis) of tl occipital artery anastomose deep to it, and its nerves enter it. As approaches its insertion its fibres lie over the supraspinatus, a fati pad being interposed.
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Action .—The cervical fibres, acting from their origin, elevate tl outer end of the clavicle and the point of the shoulder. Acting froi
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Fig. 689. —Dissection to show Muscles on Back of Neck.
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Insertion and Posterior Border of the Sterno-mastoid.—This muscle nserted into (1) the outer surface of the mastoid process of the poral bone, and (2) the superior nuchal line of the occipital bone r about its outer half, or more. The posterior border of the $cle forms the anterior boundary of the posterior triangle of the k, and has the following nerves related to it: (1) the lesser occipital snds along it to the head; (2) the great auricular passes upwards
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THE HEAD AND NECK
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1145
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r insertion they extend the head, and incline the neck towards same side, the face being directed towards the opposite side.
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The anterior border of the muscle forms the posterior boundary he posterior triangle of the neck.
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)ccasionally a small muscle, called the transversus nuchse, is met with, nding from the external occipital protuberance to the tendon of insertion le sterno-mastoid. It may be fleshy or tendinous.
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Cut. Muscles Longiss. Cap. Semispin. Cap.
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Splenius Cerv. Levator Scap.
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Semisp. Cap. Sterno-mastoid Splenius Cap.
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A MANUAL OF ANATOMY
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and forwards superficial to it towards the lobule of the auricle; (3) anterior cutaneous nerve of the neck crosses it in a forward directi (4) the accessory appears from behind it, along with the branc of the third and fourth cervical nerves to the trapezius; and (5) supraclavicular branches of the cervical plexus emerge from unt neath it.
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Some deep cervical lymph glands are situated along the poste border of the sterno-mastoid muscle. They will be described h (see p. 1199).
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The levator scapulae, rhomboids, serratus posticus super splenius, semispinalis capitis, longissimus cervicis, longissimus cap: semispinalis cervicis, intertransversales, and interspinales muscles be found described in connection with the muscles of the back 1 p. 400 et seq.).
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Second and Third Parts of the Occipital Artery. —At the mast process this vessel lies very deeply. Having crossed the rectus cap lateralis muscle, it enters the occipital groove on the inner aspeci the mastoid process, where it is covered by the following structu in order from the surface inwards: (1) sterno-mastoid; (2) spier capitis; (3) longissimus capitis; (4) mastoid process; and (5) posterior belly of the digastric. In its backward course the ve rests in succession upon the insertions of the obliquus capitis supe and semispinalis capitis, and it escapes from beneath the musi covering it in the following order: posterior belly of the digast longissimus capitis, splenius capitis, and sterno-mastoid. A emerging from beneath the last-named muscle, it lies for a little the posterior angle close to the apex, and then, frequently pierc the occipital origin of the trapezius, it enters upon the third pari its course. This part ascends along with the greater occipital ne to the occipital region, where it divides into several long tortu branches (Figs. 690 and 691).
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Branches. —The branches of the second and third parts are follows: mastoid, meningeal, descending, communicating, muscu and occipital. The mastoid branch passes through the mast foramen when there is one on the outer surface of the mastoid proc and supplies the diploe and mastoid air-cells, as well as the adjac dura mater. The meningeal branches enter the cranial cavity throi the jugular foramen, and take part in the supply of the dura me of the posterior fossa. The descending branch (arteria princeps cervi< arises under cover of the splenius capitis, and at the outer bor of the semispinalis capitis it divides into a superficial and deep brar The superficial branch is distributed to the splenius capitis and trapez and anastomoses in the latter muscle with the superficial brand the transverse cervical artery. The deep branch passes deep to semispinalis capitis, and anastomoses upon the semispinalis cerv. with (1) the deep cervical artery, a branch of the costo-cervical tm and (2) branches of the vertebral artery. The communicating branc enter the suboccipital triangle, where they anastomose with branc
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THE HEAD AND NECK
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the vertebral artery. The muscular branches supply the contiguous iscles. The occipital branches, which are the terminal branches,
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at first two in number, but these soon divide into several long
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tuous branches, which supply the occipital belly of the occipitontalis and the integument as high as the vertex. They anastomose
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g. 690. — To show Course of Occipital Artery (OA) as a Dotted Line on
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the Under Side of Skull.
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passes deep to mastoid process and muscles attached to this (digastric, longissimus capitis, sterno-mastoid, and splenius). It is lateral to rectus lateralis (RL), rectus major (R.Mj), superior oblique (SO), and semispinalis capitis (SSC). It emerges between splenius and trapezius (T).
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th one another, with the posterior auricular, the posterior branch the superficial temporal, and their fellows of the opposite side.
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The occipital venous plexus communicates with the posterior iricular and the posterior branch of the superficial temporal veins, receives the parietal emissary vein, which emerges through the
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A MANUAL OF ANATOMY
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parietal foramen, and so a communication is established with t] superior sagittal sinus; a communication is also formed with tl sigmoid sinus by means of the mastoid emissary vein through tl mastoid foramen. Sometimes it receives a small occipital emissa\ vein which emerges through an opening at the external occipit protuberance, and then a communication would be established wii the confluence of the sinuses.
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Two or three occipital veins leave the occipital plexus. Tl external vessel is known as the posterior external jugular vein. Havii
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been reinforced by tributaries from the superficial structures at tl upper part of the back of the neck, the posterior external jugular ve passes on to the sterno-mastoid, where it opens into the extern jugular. The middle occipital vein (inconstant) accompanies tl occipital artery, and usually opens into the internal jugular. Tl internal occipital vein, having in some cases pierced the trapeziu passes beneath the semispinalis capitis, and enters the suboccipit triangle. In this situation it joins the suboccipital plexus, from whi( the deep cervical and vertebral veins emerge.
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Occipital Lymph Glands. —These glands are usually two in numbe and he superficial to the occipital portion of the trapezius, or the upp part of the semispinalis capitis. They receive their afferent lymphati from the back part of the scalp, and their efferent lymphatics pass the deep cervical glands.
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Deep Cervical Artery. —This vessel is in most cases a branch of tl costo-cervical trunk of the second part of the subclavian. Havii passed backwards between the transverse process of the seveni cervical vertebra and the neck of the first rib, it ascends upon tl semispinalis cervicis, under cover of the semispinalis capitis, towar< the level of the spine of the axis, where it anastomoses with the de( branch of the ramus descendens of the occipital. In its course furnishes a spinal branch, which enters the vertebral canal throu^ the intervertebral foramen for the eighth cervical nerve, and mu cular branches, which anastomose with branches of the vertebr artery.
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The deep cervical vein begins within the suboccipital triangle the suboccipital plexus, which receives the internal occipital vei It descends in company with the deep cervical artery to the low' part of the neck, where it passes forwards between the transver: process of the seventh cervical vertebra and the neck of the first ri and ends by joining the vertebral vein just before that vessel terminate in the innominate vein.
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In addition to the muscular branches of the occipital and dee cervical arteries, the deep muscles of the back of the neck receh twigs from the second part of the vertebral artery, which travers* the foramina transversaria of the upper six cervical vertebrae. The: twigs pass backwards through the intertransverse spaces, and anas! mose with branches of the ramus descendens of the occipital artei and the deep cervical artery.
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THE HEAD AND NECK
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1149
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Suboccipital Region—Muscles—Rectus Capitis Posterior Major
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Origin .—The ridge leading to one of the tubercles in which the ne of the axis ends.
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Insertion .—The outer part of the inferior nuchal line of the occipital ne, and the subjacent area.
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Nerve-supply .—The posterior primary ramus of the suboccipital rve.
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The direction of the fibres is upwards and outwards, in spite of its ime.
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Action. —(1) To rotate the face towards the same side; and (2) to tend the head.
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A MANUAL OF ANATOMY
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The muscle is pyramidal, and its insertion is largely covered the obliquus capitis superior.
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Rectus Capitis Posterior Minor— Origin.— The posterior arch the atlas close to the tubercle.
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Insertion. —The inner third of the inferior nuchal line of the occipi bone, and the subjacent area as low as the foramen magnum.
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Nerve-supply .—The posterior primary ramus of the suboccipi nerve.
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The direction of the fibres is upwards in an expanded manner.
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Action. —To extend the head.
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The muscle is fan-shaped, and lies deeper than, and medial the rectus capitis posterior major.
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Obliquus Capitis Inferior — Origin.- —The outer and upper aspect the spine of the axis.
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Insertion. —The lower surface of the transveise process of the at at its back part.
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Nerve-supply. —The posterior primary ramus of the suboccipi nerve.
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The direction of the fibres is outwards and slightfy upwards.
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Action .—To rotate the atlas along with the head, so that the fa looks towards the same side.
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The muscle is thick and fleshy. At its origin it is interpos between the rectus capitis posterior major superiorly and the high bundle of the semispinalis cervicis interiorly. The greater occipi nerve winds round its lower border.
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Obliquus Capitis Superior — Origin. —The upper surface of the trai verse process of the atlas at its back part.
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Insertion .—The occipital bone between the outer parts of i superior and inferior nuchal lines.
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Nerve-supply. —The posterior primary ramus of the suboccipi nerve.
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The direction of the fibres is upwards and very slightly inwards.
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Action .—(1) To extend the head, and (2) to act as a slight late flexor of the head.
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The muscle is triangular.
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Suboccipital Triangle. —This triangle is situated under cover of 1 upper part of the semispinalis capitis close below the occipital bone.
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Boundaries — Supero-medial. —The rectus capitis posterior maj External. —The obliquus capitis superior. Inferior. —The obliqi capitis inferior. The roof is formed by the semispinalis capitis a longissimus capitis, and the floor by half of the posterior arch the atlas and half of the posterior atlanto-occipital membrane. * contents are (1) the third part of the vertebral artery, (2) the si occipital plexus of veins, and (3) the posterior primary ramus of first cervical nerve. The greater occipital nerve turns upwards rou the inferior oblique and crosses the inner part of the triangle deep the semispinalis capitis, and the deep division of the ramus descend* of tde occipital artery runs down near this.
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THE HEAD AND NECK
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1151
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lird Part of the Vertebral Artery. —The vertebral artery, having i through the foramen transversarium of the atlas, enters upon bird part of its course, and takes a winding course backwards
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Recti Capitis Posteriores Minores
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Rectus Capitis Posterior Major
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Tubercle on Posterior Arch of Atlas
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Spine of Axis-
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Interspinales
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,Suboccipital Triangle
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Obliquus Capitis Superior
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’-.Mastoid Process
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Vertebral Artery (Third Part)
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Posterior Primary Ramus of Suboccipital Nerve ' Transverse Process of -- Atlas
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* Obliquus Capitis Inferior Greater Occipital Nerve
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Semispinalis Cervicis (upper two bundles)
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Fig. 692.—The Suboccipital Triangle.
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inwards. It lies in the vertebrarterial groove of the atlas, the
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rior primary ramus of the first cervical nerve being beneath it,
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it passes under an arched band of the posterior atlanto-occipital
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693.—Atlas seen from Above, to show Position of Vertebral Artery
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and Suboccipital Nerve.
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hrane, which is sometimes ossified. It thus leaves the suboccipital igle, pierces the dura mater, and enters the cranial cavity through oramen magnum. The third part of the vessel furnishes muscular
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A MANUAL OF ANATOMY
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branches to the adjacent muscles, which anastomose with the rai descendens of the occipital and the deep cervical of the costo-cerv trunk.
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Suboccipital Plexus of Veins. —This plexus is formed by bram which proceed from (i) the vertebral venous plexuses, (2) the adjat muscles, and (3) the occipital periosteum. It receives the inte: occipital vein, and the blood is conveyed away from it by the d cervical vein, already described, and the vertebral vein, which wil afterwards considered.
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Posterior Primary Division of the First Cervical or Suboccii Nerve. —This division passes backwards as a single nerve in the ve brarterial groove of the atlas, lying between the bone and the tl part of the vertebral artery. On entering the suboccipital triangl divides into branches which supply the obliqui, recti posteriores, semispinalis capitis muscles. A filament joins the greater occip nerve.
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Posterior Primary Rami of the Cervical Spinal Nerves.—
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cervical nerves are eight in number, the first being known as the s occipital nerve. Each breaks up into an anterior and a poste primary ramus. The posterior primary ramus of the first or s occipital is single, and has just been described. The posterior prim rami of the lower six arise in the intervertebral foramina, and e soon divides into a lateral and medial branch. The upper two cerv nerves make their exit behind the articular masses, and their poste primary rami cross the vertebral arches behind these; the second div: into medial and lateral branches. The lateral branches of all are tributed to the deep muscles, and do not become cutaneous. medial branch of the posterior primary ramus of the second, whic of large size, constitutes the greater occipital nerve. It winds nr the lower border of the obliquus capitis inferior, and pierces semispinalis capitis, to which it gives branches. Later it r pierce the trapezius to reach its cutaneous distribution, which been already described. The medial branches of the third, fou: and fifth are directed inwards superficially to the semispin cervicis, to which, as well as to the semispinalis capitis, they { branches. Close to the cervical spines they pass backwards me^ to the spinalis capitis (biventer cervicis), and, having pierced splenius and trapezius, they reach the integument, which they sup] The medial branch of the posterior primary ramus of the third, be] piercing the trapezius, gives off a small ascending branch, knowr the third occipital. It passes upwards, lying at first under cove: the trapezius, and then passing through it to reach the occipital inte ment. The medial branches of the posterior primary rami of sixth, seventh, and eighth are directed inwards towards the cerv spines beneath the semispinalis cervicis, and are distributed to adjacent muscles. They do not furnish any branches to the inte ment.
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THE HEAD AND NECK
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ii53
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The Scalp and Temporal Region.
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ascise. —The place of the deep fascia beneath the skin may be to be taken by the epicranial aponeurosis of the occipito-frontalis
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le. The aponeurosis becomes thin and fascial over the temporal
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ns. Where it is thick and aponeurotic it is firmly attached to overlying skin by fibrous processes, between which are small r lobules, so that the subcutaneous laver is firm and somewhat ular in appearance. The vessels and nerves are distributed in this
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, which loses its fibrous nature in the temporal regions and becomes
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lerficial soft fatty layer.
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uperficial Nerves and Vessels. —The superficial nerves of the ero-lateral aspect; the greater, small, and third occipital nerves; the mastoid branch of the great auricular , have been described idy. In the fronto-parietal region two sensory nerves are met —namely, the supra-orbital and supratrochlear —both of which lerived from the frontal nerve, which is one of the branches of the
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halmic division of the fifth cranial nerve. In the temporal region
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the temporal branches of the facial nerve , the auriculo-temporal
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1 n
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u 6 Uf.
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Y «r
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Skull
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Fig. 694.—Diagram of Section through Scalp.
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e, and the zygomatico-temporal nerve. Of the arteries of the p, the third part of the occipital artery, in the posterior region, has 1 described. Those of the fronto-parietal region are three in ber—namely, the supra-orbital , supratrochlear , and anterior branch he superficial temporal. The superficial temporal artery ramifies he side of the head in the temporal region.
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Qie supra-orbital nerve, which is of large size, leaves the orbit •ugh the supra-orbital foramen. It then ascends, lying at first ) to the upper part of the orbicularis oculi and the frontal belly he occipito-frontalis muscle, but subsequently piercing the latter cle in two branches, medial and lateral. The lateral branch is the er of the two, and its offsets extend as far back as the lambdoid ire. As the supra-orbital nerve passes through the supra-orbital 'h it furnishes one or two twigs to the mucous membrane of the tal sinus and to the diploe of the frontal bone, and after leaving notch it sends downwards branches to the integument of the upper id. After this the nerve supplies the integument of the frontoetal region.
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rhe medial and lateral branches of the supra-orbital nerves sometimes leave orbit separately, and each may form a notch or foramen of its own.
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A MANUAL OF ANATOMY
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1154
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The supratrochlear nerve, which is of small size, is medial to supra-orbital nerve. It leaves the orbit close to the medial angi process of the frontal bone, where it lies above the pulley of the s-upe oblique muscle of the eyeball. It then ascends deep to the upper j of the orbicularis oculi and the frontal belly of the occipito-front muscle, and, piercing the former muscle, it has a limited distribui to the frontal integument close to the median line. As the nt leaves the orbit it furnishes twigs to the inner part of the integurr of the upper eyelid.
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The supra-orbital artery is a branch of the ophthalmic, and emei from the orbit with the supra-orbital nerve. It is distributed to structures covering the frontal bone, and anastomoses with the su] trochlear branch of the ophthalmic artery and the anterior brand the superficial temporal artery. In the supra-orbital notch it fumis one or two branches to the mucous membrane of the frontal sinus to the diploe of the bone, and after leaving the notch it sends do wards branches to the integument of the upper eyelid (Fig. 698).
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The supra-orbital vein passes downwards and inwards to a p( just above the medial angle of the orbit, where it joins the suj trochlear vein. In this manner the angular vein is formed, whic the commencement of the anterior facial vein. The supra-orbital ^ receives tributaries from the frontal region and the upper eyelid, ; in the region of the medial angle of the orbit it communicates with superior ophthalmic vein. It also communicates with the supe ophthalmic vein through the supra-orbital notch, and this commun tion receives the frontal diploic vein, which returns the blood from diploe of the frontal bone and mucous membrane of the frontal sir
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The supratrochlear artery (frontal artery), like the supra-orbita a branch of the ophthalmic, and leaves the orbit with the supratroch. nerve. It is distributed to the structures over the frontal bone me* to the supra-orbital artery, with which it anastomoses, as well as v its fellow of the opposite side.
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The supratrochlear vein (frontal vein), of large size, passes do wards near the median line, and at a point just above the medial ar of the orbit is joined by the supra-orbital vein, the resultant ve being the angular vein. At the root of the nose it communicates v its fellow of the opposite side by a transverse vessel, called the m arch.
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The supra-orbital and supratrochlear veins communicate with e other, and with the tributaries of the anterior branch of the superfi temporal vein.
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Occipito-frontalis. —This muscle consists of the following pa (1) two occipital bellies, (2) two frontal bellies, and (3) the epicra aponeurosis.
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Each occipital belly arises from (1) the highest nuchal line of occipital bone; and (2) the outer surface of the mastoid process of 1 temporal bone immediately above the insertion of the sterno-mas muscle.
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THE HEAD AND NECK
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ii55
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Insertion .—The epicranial aponeurosis.
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Each belly forms a thin, broad sheet, the length of the fasciculi Lg about ij inches. The two bellies, right and left, are separated ards the median line by a portion of the epicranial aponeurosis, ch here dips down between them.
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Each frontal belly, right and left, is separated superiorly by a row angular portion, of the epicranial aponeurosis, but interiorly / are in contact. Origin .—(1) The subcutaneous tissue of the
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Fig. 695.—To show Occipital Belly of Occipito-frontalis.
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)row and root of the nose, where the fibres blend with the upper - of the orbicularis oculi and the corrugator supercilii; and (2) slightly 1 the zygomatic process of the frontal bone, and from the nasal
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e.
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Insertion ,—The epicranial aponeurosis a little below the level of fronto-parietal suture.
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Hie fasciculi are about 3^ inches long, and the innermost fibres riorly are regarded by some as being prolonged downwards upon nasal bone as the procerus muscle.
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A MANUAL OF ANATOMY
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1156
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Epicranial Aponeurosis. —This is the intermediate tendon of occipito-frontalis muscle. It forms an aponeurotic stratum ben< the superficial fascia, and is connected firmly to the skin by fib processes, which separate the subcutaneous tissue into lobules, deep surface is loosely connected by areolar tissue to the subja* periosteum. Posteriorly it gives insertion to the two occipital be and in the interval between these it dips down to be attached to inner part of the superior nuchal line of the occipital bone and external occipital protuberance. Anteriorly it gives insertion to two frontal bellies. Laterally, below the superior temporal : it is prolonged downwards over the temporal fascia as a deh
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Fig. 696. —Shows Frontal Portion of Occipito-frontalis.
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expansion, which gives origin to the auricularis superior and auricul anterior muscles. It is connected to the superior temporal line I thickening of the loose areolar tissue between it and the bone.
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Nerve-supply .—Each occipital belly is supplied by the poste auricular branch of the facial nerve, and each frontal belly is supp by the temporal branches of the facial nerve.
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Action .—The two occipital bellies draw backwards the epicra aponeurosis, and along with it the scalp. The two frontal bellies from above, elevating the eyebrows, and throwing the skin of frontal region into transverse wrinkles. When the occipital and fro' bellies act simultaneously the scalp is drawn backwards, and eyebrows are forcibly raised. In certain cases the frontal bellies 1
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THE HEAD AND NECK
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ii57
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n the reverse direction, their lower attachment being fixed by other muscles, such as the orbicularis oculi, corrugator supercilii, and crus. When this is done the scalp may be alternately twitched r ard and backward, a simian habit which may be acquired by
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tice.
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Pericranium. —This is the periosteum of the cranium, and it is sly connected by areolar tissue to the superjacent epicranial leurosis.
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Parotid Duct. Buccinator Muscle_
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Facial Artery Submental Artery
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Lingual Artery Sup. Lar. Art. and Nerve Thyro-hyoid Muscle Superior Thyroid Artery
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Inf. Belly of Omo-hyoid
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Subclavian Artery (third part)
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Transverse Facial Artery
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Superficial Temporal Artery
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- Maxillary Artery
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Posterior Auricular Artery
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Occipital Artery
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-Stylo-hyoid Muscle
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-Post. Belly of Digastric
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-Hypoglossal Nerve
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-Nervus Descendens
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Cervicalis External Carotid Artery
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Stemo-mastoid — Trapezius
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_Transverse Cervical Artery
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-.Suprascapular Artery
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Fig. 697. —The Left Side of the Head and Neck. The platysma has been removed.
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The temporal branches of the facial nerve pass upwards a little in tt of the auricle, and supply the following muscles: the frontal Y of occipito-frontalis, upper part of the orbicularis oculi, corrusupercilii, auricularis superior and auricularis anterior. They municate with the auriculo-temporal, zygomatico-temporal, and 'a-orbital nerves.
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Hie auriculo-temporal nerve is a branch of the mandibular nerve, 'h is the third division of the fifth cranial nerve. It emerges just nd the capsule of the mandibular joint, turns upwards round the of the zygoma, and ascends immediately in front of the auricle in
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A MANUAL OF ANATOMY
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1158
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company with the superficial temporal artery, lying between that, ves and the auricle
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Branches.—In this part of its course the nerve furnishes following branches! (1) two branches to the external auditory meat which enter the canal between its osseous and cartilaginous walls, a supply the integument of the meatus, the upper of the two branc. giving an offset to the tympanic membrane; (2) two auricular brand which supply the skin of the tragus and outer aspect of the auri over less than its upper half; and (3) superficial temporal brand which supply the integument above and in front of the auricle, and the temporal region generally.
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The zygomatico-temporal nerve (temporal branch of temporo-ma nerve) from the maxillary is of small size, and pierces the tempc fascia about 1 inch above the anterior part of the zygoma, and cl behind the frontal process of the zygomatic bone. Having cc municated with one of the temporal branches of the facial nerve has a limited distribution to the integument of the anterior part the temporal region.
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The superficial temporal artery is one of the terminal branches the external carotid artery, from which it arises within the pare gland on a level with the neck of the mandible. Leaving the gla it ascends in front of the auricle in company with the auriculo-tempc nerve, which lies between the vessel and the auricle, and after a cou of about 2 inches it divides into its two terminal branches.
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Branches.—These are as follows: (1) transverse facial; (2) articul (3) auricular; (4) middle temporal; (5) zygomatic; and (6) termina namely, anterior and posterior.
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The transverse facial artery will be described in connection w the face. It arises within the parotid gland, and in its course furnis glandular branches. The articular branches supply the mandiby joint. The auricular branches supply the outer aspect of the auri' and in part the external auditory meatus. The middle tempc artery pierces the temporal fascia immediately above the zygoma, c then ascends in a groove on the outer surface of the squamous p of the temporal bone deep to the temporalis. It gives branches to temporalis, and anastomoses with the deep temporal branches of maxillary artery. The zygomatic artery passes forwards close above zygoma, where it lies between the two layers of the temporal fas< It is distributed to the outer part of the orbicularis oculi muscle, anterior branch passes forwards and upwards in a tortuous man: and is distributed to the structures covering the frontal bone, wher anastomoses with the supra-orbital and supratrochlear branches 0T ophthalmic artery, and with its fellow of the opposite side, posterior branch takes an arched course upwards and backwa above the auricle, supplying the adjacent structures, and anas mosing with the posterior auricular and occipital arteries, and v its fellow of the opposite side (see Fig. 698).
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The arteries of the scalp are peculiar in many ways. In the f
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THE HEAD AND NECK
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ii59
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they are very superficial, lying in the fatty layer of the scalp
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deep to the skin; they are thus very liable to injury, and in old le, where their walls are hardening and the superficial fat diminishthey may easily be seen in the temporal region, n the second place they are very tortuous, a condition which is lly associated with arteries supplying movable parts, and in ige this tortuosity increases.
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'hirdly, they not only anastomose with one another, as most 'ies do, but they anastomose freely across the middle line, thus lg wonderful vitality to a piece of scalp which has been torn away >st completely.
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L. Testut’s ‘ Anatomie Humaine ’).
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fourthly, when cut they bleed most profusely, because their walls prevented from collapsing by the dense connective tissue between skin and the epicranium in which they lie. For this reason, too, difficult to pick them up when they have to be tied, fhe superficial temporal vein is formed in front of the auricle by union of an anterior and a posterior branch, the former communing freely with the supra-orbital and supratrochlear veins, and the T with the posterior auricular vein and the occipital venous plexus, ve the zygoma it is joined by the middle temporal vein, which inates in a plexus in the temporal fossa, and pierces the temporalis temporal fascia, receiving in its course the zygomatic vein. The Official temporal vein then descends over the zygoma and enters
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n6o
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A MANUAL OF ANATOMY
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the parotid gland, within which it receives the auricular, articu and transverse facial veins. Finally, it joins the maxillary vein ah the level of the neck of the mandible to form the posterior facial's (temporo-maxillary vein).
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Extrinsic Muscles of the Auricle.—These are three in number, follows: (i) auricularis superior; (2) auricularis anterior; and (3) aur: laris posterior.
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Auricularis Superior (Attollens Aurem)— Origin. —The lateral par the epicranial aponeurosis and temporal fascia.
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Insertion. —The inner or cranial surface of the auricle over convexity corresponding to the fossa of the antihelix on its 01 surface.
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Nerve-supply. —The temporal branches of the facial nerve, posterior part of the muscle may be supplied by the posterior aurici branch of the facial nerve.
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The muscle is very thin, pale, and fan-shaped, and. its fibres c verge in a downward direction.
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Action. —To raise the auricle, though all the auricular muscles vestigial in man and practically functionless.
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Auricularis Anterior (Attrahens Aurem)— Origin .—The lateral p of the epicranial aponeurosis in front of the auricularis superior, v which muscle it is continuous. Also from the temporal fascia.
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Insertion. —The anterior part of the helix of the auricle.
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Nerve-supply. —The temporal branches of the facial nerve.
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The muscle is directed backwards.
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Action. —To draw forwards the auricle.
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Auricularis Posterior (Retrahens Aurem)— Origin. —The upper p of the outer surface of the mastoid process of the temporal bone.
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Insertion. —The inner or cranial surface of the auricle over convexity of the concha.
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Nerve-supply. —The posterior auricular branch of the facial nerv
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The muscle is directed forwards.
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Action. —To draw back the auricle.
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The auricularis posterior is more distinct than the other two muse and is usually arranged in two bundles.
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Behind the ear, in the mastoid region, which is not a part of scalp proper, there are certain structures which have some conned with the scalp. These comprise posterior auricular nerves (branc of the facial and vagus), posterior auricular vessels, and poste auricular lymph glands.
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Posterior Auricular Nerve.—This is a branch of the facial ne; immediately after it emerges from the facial canal through the st; mastoid foramen. It passes upwards between the mastoid pro< and the auricle, where it lies deeply in company with the postej auricular artery, and it divides into two branches—auricular ; occipital. The auricular branch supplies the auricularis poste; muscle on its deep aspect, and those intrinsic muscles of the aur which lie on its inner or cranial aspect. It may also send a bra
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THE HEAD AND NECK
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1161
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yards beneath the auricularis posterior to supply the posterior t of the auricularis superior. The occipital branch passes back■ds, lying deep to the lesser occipital nerve and posterior branch the great auricular, and supplies the corresponding half of the ipital belly of the occipito-frontalis muscle. The posterior auricular ve communicates with the lesser occipital and great auricular ves, and also with the auricular branch of the vagus.
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The Auricular Branch of the Vagus Nerve (Nerve of Arnold). —This t branch of superior ganglion of the nerve. Having traversed the stoid canaliculus in the petrous part of the temporal bone, it srges through the tympano-mastoid fissure between the mastoid cess and tympanic plate, and then divides into two branches. One nch takes part in the supply of the inner or cranial surface of the icle, and also supplies the lower and back part of the external litory meatus; and the other branch joins the posterior auricular ve.
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Posterior Auricular Artery. —This vessel is one of the two posterior nches of the external carotid artery, the other branch being the ipital artery. Having passed backwards and upwards on the loid process under cover of the parotid gland, it lies deeply between i mastoid process and the auricle in close relation to the posterior icular nerve, and divides into two branches—auricular and occipital, e auricular branch supplies the inner or cranial surface of the auricle i adjacent structures, and it anastomoses with the posterior branch the superficial temporal artery. The occipital branch passes backrds to the occipital belly of the occipito-frontalis muscle, and istomoses with the occipital artery.
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The posterior auricular vein is of fairly large size, and returns the od from the lateral portion of the scalp posteriorly and the inner face of the auricle. Its radicles communicate with the occipital xus and with the posterior branch of the superficial temporal vein, e vessel passes downwards and forwards over the upper part of the rno-mastoid muscle, and terminates on this muscle about the level the angle of the mandible by joining the posterior division of the sterior facial vein to form the external jugular vein.
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Mastoid Lymph Glands (Posterior Auricular Lymph Glands). These all glands lie close to the insertion of the sterno-mastoid muscle, ey receive their afferent lymphatics from the lateral part of the back the scalp and the back of the auricle, and their efferent lymphatics $s to the upper deep cervical lymph glands.
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Temporal Fascia. —This is a strong aponeurosis which covers the nporalis. Superiorly it is attached from before backwards to the nporal border of the zygomatic bone, the superior temporal line of i frontal and parietal bones, and the supramastoid crest. of the nporal bone. Interiorly it divides into two laminae, which aie ached to the outer and inner margins of the upper border of the somatic arch. Between these two laminae there are a small amount adipose tissue, and the zygomatic branch of the superficial temporal
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1162
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A MANUAL OF ANATOMY
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artery, and the zygomatico-temporal nerve. Superficial to the fasc there are the delicate prolongation of the lateral portion of the e] cranial aponeurosis and the auriculares superior et anterior muscl< with the superficial temporal vessels and auriculo-temporal nen Superiorly the fascia gives origin by its deep surface to superfic: fibres of the temporalis, but it is separated from that muscle towar the zygoma by fat.
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The temporalis muscle is described on p. 1302.
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Lymphatic Vessels of the Scalp—Frontal Region. —These pass the parotid lymph glands. The anterior lymphatics pass directly the parotid lymph glands, and the posterior lymphatics terminate in t mastoid lymph glands.
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The Scalp as a Whole. —Before leaving the scalp it may be w< to review its general structure and to notice that it is made up of fi layers.
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(1) The skin is very thick, and nee^6 a firm incision to penetrate:
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(2) The subcutaneous tissue binds the skin closely to the epicrani aponeurosis, with which it moves; it contains lobular, granulated f in which are the bloodvessels and nerves as well as the roots of t. hair follicles. On account of the presence of the nerves as well as of t. density of the connective tissue any suppuration in this layer will strictly localized and very painful.
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(3) The epicranial aponeurosis is formed by the very thin, flatten tendon of the occipito-frontalis muscle.
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(4) The subaponeurotic layer, sometimes known to surgeons as t. ‘ dangerous layer * of the scalp, is composed of very loose connectf tissue, and is little more than a lymph space. The looseness of tj cellular tissue allows the first three layers to move freely over t] skull, and if septic matter reaches it and suppuration follows, t] pus readily spreads all over the space and tends to bag at the mo dependent points in front and behind. The absence of nerves and tl looseness of the tissue account for the little pain which accompani suppuration in this layer.
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(5) The periosteum or pericranium covers the skull bones, and continuous with the dura mater at the sutures as long as these a unclosed. For this reason a subpericranial collection of blood pus will be limited to the area of one skull bone, while a subepicrani collection, as has been seen, has no such definition.
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Basal Part of the Cranial Cavity.
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Dura Mater on the Base of the Skull. —A full and general accoui of the membranes of the brain will be found on p. 1598 ^ se ^-> short description of the dura mater, as it is seen on the base of tl skull after removal of the brain, will be given here.
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The dura mater is seen to be continuous with the falx cerebri in t middle line in front. Just outside this it covers the cribriform pla of the ethmoid at the bottom of a well-marked hollow which contai
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THE HEAD AND NECK
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1163
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olfactory bulb. External to this it covers the irregularities of the tal plate of the frontal and the lesser wing of the sphenoid behind . In the middle fossa it lines the so-called ‘ optic groove/ and at
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I end of this is carried into the optic foramina. Behind the groove >rms the diaphragma sella, covering the hypophyseal fossa, while
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pierced by the internal carotid artery just behind the foramen.
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diaphragma sellae shows a central hole for the infundibulum of hypophysis cerebri. The membrane is attached to the clinoid
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esses and the interclinoid ligaments, and stretches outwards from
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e to line the hollow of the greater wing and upper surfaces of the
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•ous bone. It is carried upwards and forwards here to cover the erior orbital fissure and gain the lower aspect of the lesser wing, mall fold of dura mater projects from the edge of the lesser wing he sphenoid, the sphenoidal fold , and a small ‘ lunula ’ overhangs optic foramen. At the upper border of the petrous bone the nbrane projects upwards and inwards as the tentorium cerebelli, ch is a two-layered reflection of the dura mater. Below the torium it lines the posterior fossa, and presents apertures through ch all the nerves which come from the pons and medulla pass to
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h their bony foramina. A small fold, the falx cerebelli, projects
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he middle line behind. The dura mater becomes continuous with spinal dura at the foramen magnum, but the exact position of this mien is not easily distinguished when the membrane is in position, ng to the smooth, continuous slope formed by it as it passes from basi-occiput over the odontoid process and its ligaments into the tebral canal.
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Certain structures lie deep to the dura mater, between it and the y skull— i.e., between the inner layer, which we have been consider, and the outer layer, which covers the bones. These are venous ises, nerves, and arteries. The venous sinuses on the base of the
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II are (see p. 1603 et seq. for further details):
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The sigmoid, running downwards and then forwards in the posterior >a to reach the jugular foramen.
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The inferior petrosal, passing forwards and upwards from the ular foramen to the apex of the petrous bone along its lower edge. The superior petrosal, running forward along the upper edge of the rous bone at the base of the tentorium cerebelli.
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The cavernous, placed on the side of the body of the sphenoid ere this joins the greater wing, and formed by the junction of the ) petrosal sinuses; in front it is continuous with the superior ophImic vein and with the spheno-parietal sinus, which lies in the fold lura mater along the lesser wing of the sphenoid.
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The circular sinus is a spongy venous network which surrounds
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pituitary body and connects the two cavernous sinuses.
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The transverse sinus lies under the central basal dura mater, and n the form of a network joining the inferior petrosal sinuses.
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The cranial nerves must necessarily pierce the dura mater to ch and pass through the base of the skull, and the situations of the
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A MANUAL OF ANATOMY
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points of passage through the membranous and bony parts do n always correspond. Those nerves which leave the skull in relati( with the greater wing of the sphenoid pass through the dura mat at points some distance behind their bony foramina, and in the inte vening parts of their courses lie deep to the inner layer of dura mate lying near or in relation with the cavernous sinus. These nerv
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Frontal Sinus
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Anterior Fossa
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Optic Nerve Ophthalmic Artery
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Oculo-motor Nerve / •
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Trochlear Nerve
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Region of Cavum Trigeminale
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Trigeminal Nerve
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Facial Nerve
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Auditory Nerve
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G losso-pharyngeal Nerve
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Vagus Nerve
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Posterior Border c Small WingofSphi
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Ant. Intercav., S: Hypophysis C«
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.-Cavernous S -- Abducent N
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— Middle Foss
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4 - - Basilar Plex
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Sup. PetrosE Sinus
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Inf. Petrosa] Sinus
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" Sigmoid Sin
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'•Cerebellar Fossa
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Accessory Nerve
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Transverse Sinus
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Hypoglossal Nerve]
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Cerebral Fossa
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Spinal]Cord j Confluence of Sinuses Occipital Sinus
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Fig. 699. —The Internal Base of the Skull, showing the Cranial Nervi
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and Venous Sinuses.
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are the oculo-motor, trochlear, trigeminal, and abducent; the oth< cranial nerves pierce the dura mater opposite their bony foramina.
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It is not quite correct to say that the cranial nerves ‘ pierce ’ the dura mat at the places where their apertures of exit are seen; they carry out with the a covering from the membrane, so that they could be described rightly 1 evaginating it. The covering layer, however, is so thin in most cases, and so soon lost in the ordinary fibrous sheath of the nerve, that little exceptk is taken to the descriptive expression ‘ piercing.' In the case of the trigemin nerve, however, the evaginated covering of dura mater is better marked, and '
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THE HEAD AND NECK
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1165
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he whole, looser; it envelops the roots of the nerve and the trigeminal
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jlion, and is known as the cavum trigeminale (.Meckel's cave). The cavum jminale, therefore, lies between the dura and the skull. The optic nerve, eover, should not be described as ‘ piercing ’ the membrane, for the eye and lervous stalk are developmentally parts of the brain itself, and the dura er is carried along the nerve to become directly continuous with the sclerotic
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of the eye, which represents the same layer.
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Some other nerves, such as the superficial petrosals and the nasoiry in a part of its course, lie deep to the dura mater, and will be bribed later.
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All the meningeal vessels lie between skull and dura mater, and do pierce the inner membranous layer. The only things which pass Dugh this layer are the cranial nerves and the cerebral vessels; $e last are represented by (a) the internal carotid, which, lying irst between dura and bone with the cavernous sinus, pierces the nbrane medial to the anterior clinoid process to reach the brain;
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. ( b ) the vertebral arteries, which pierce the membrane below the 11 and run up through the foramen magnum to reach the brain, tain cerebral veins pierce the dura mater at various points (see p. 8 ) to open into extradural sinuses.
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Hie aqueduct of cochlea is described as passing through the dura to reach subarachnoid space, and the endolymphatic duct lies between the membrane the bone.
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Cranial Nerves at the Base of the Skull. —The cranial nerves are inged in twelve pairs, and as they leave the cranial cavity they five sheaths from the meninges of the brain.
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The olfactory bulb rests upon one half of the cribriform plate of ethmoid bone, with dura mater interposed. Through the fora1a of that plate it receives about twenty olfactory filaments, which
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e as the axons of the olfactory cells of the olfactory mucous
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[nbrane of the nasal fossa.
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The optic nerve passes forwards and outwards from the optic asma to the optic foramen, through which it enters the orbit. It .ccompanied by the ophthalmic artery, which lies below and lateral t. Before reaching the foramen it is crossed by the anterior cerebral ery, and the internal carotid comes through the dura mater just dnd and lateral to it.
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The third or oculo-motor nerve pierces the dura mater, which ns the upper and outer wall of the cavernous sinus, a little in front the posterior clinoid process of the sphenoid bone.
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The fourth or trochlear nerve, of small size, pierces the dura mater a point a little behind the posterior clinoid process of the sphenoid ie, lateral to the third nerve, and in or just beneath the free margin the tentorium cerebelli. Afterwards it traverses the outer wall of
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cavernous sinus.
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The fifth or trigeminal nerve consists of two roots—sensory and tor. These two roots pierce the dura mater near the apex of the rous part of the temporal bone below the tentorium, and enter
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n66
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A MANUAL OF ANATOMY
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a'recess of the dura mater, called the cavurn ingeminate (Meckel's cav where they will be presently described.
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The sixth or abducent nerve pierces the dura mater £ inch behi the level of the posterior clinoid process, and near the apex of t petrous bone, where it enters the inferior petrosal sinus. It lies little to the inner side of the fifth nerve.
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The seventh or facial nerve, the eighth or auditory nerve, accoi panied by the internal auditory artery, enter the internal meatus.
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The ninth or glosso-pharyngeal nerve, the tenth or vagus ner and the eleventh or accessory nerve pass through the middle compa:
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Fig. 700.—Showing the Venous Sinuses on the Petrous Bone, and
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Relation with the Trigeminal Nerve.
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Also shows great superficial petrosal nerve.
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ment of the jugular foramen. This foramen is divided into thi compartments—namely, antero-medial, middle, and postero-later The antero-medial compartment gives passage to the inferior petro.j sinus. The middle compartment transmits the glosso-pharyngeal, vagi and accessory nerves, in this order from before backwards. T glosso-pharyngeal nerve pierces the dura mater separately, a receives special sheaths from the dura mater and arachnoid membrai The vagus and accessory nerves pass together through a sin^ aperture in the dura mater, and receive common sheaths from t dura and arachnoid membrane. The postero-lateral compartment trai
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THE HEAD AND NECK
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1167
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5 the sigmoid sinus, which terminates in the internal jugular vein, the vein is deep to the dura, this part of the foramen cannot be 1 directly when the dura mater is in position.
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The twelfth or hypoglossal nerve pierces the dura mater in two dies, which pass through separate apertures. As these bundles 5 through the anterior condylar canal they unite to form one nerve, ween the points of exit of the hypoglossal and the last three nerves jugular tubercle is seen, forming a very useful landmark.
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Structures passing through the Foramen Magnum. —(1) The medulla mgata, with its membranes, passes out and becomes the spinal i. (2) The spinal root of the accessory nerve of either side, having mded from the interval between the posterior roots of the cervical lal nerves and the ligamentum denticulatum, enters the cranial ity. It then turns outwards behind the jugular tubercle to the Idle compartment of the jugular foramen, where it meets the rial root of the nerve, with which it becomes closely connected it passes through the foramen. (3) The vertebral artery of each j enters the cranial cavity after having pierced the dura mater. The two anterior spinal branches of the vertebral arteries descend the front of the medulla oblongata, and, inclining inwards towards h other, they unite in passing through the foramen magnum to n the anterior spinal artery, the membrana tectoria, and the apical ment of the odontoid process.
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Trigeminal Ganglion (Gasserian Ganglion) (Fig. 700).—The trilinal ganglion occupies the trigeminal impression (Gasserian imssion) on the superior surface of the petrous part of the temporal Le near the apex, where its posterior part lies in a recess of the a mater, called the cavum trigeminale ( Meckel’s cave). It is someit semilunar, being convex in front and concave behind, and measures y \ inch from before backwards. It is associated with the sensory t of the fifth nerve, which, before entering the posterior concave ect of the ganglion, becomes expanded, its fasciculi at the same e becoming separated and assuming a plexiform arrangement, lially the ganglion is intimately related to the back part of the ernous sinus, and by its inner and lower aspect to the internal otid artery in the foramen lacerum, and on this aspect it receives icate filaments from the internal carotid sympathetic plexus. The tor root of the fifth nerve, small in size, lies below the deep surface
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he ganglion; but there is no blending of the two sets of fibres, the
 +
tor root passing independently in an outward direction to the imen ovale. The greater superficial petrosal nerve, on its way to foramen lacerum, passes beneath the ganglion, though not in the r um trigeminale.
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The ganglion contains cells similar to those of a spinal ganglion, 1 it receives its blood from the middle and accessory meningeal eries. It is important in connection with modern surgery to notice ■t the front part of the ganglion does not lie in the cavum trininale, but has a close investment of dura mater. Hence the front
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1168
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A MANUAL OF ANATOMY
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part may be removed without opening the subarachnoid space allowing cerebro-spinal fluid to escape.
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Branches. —The branches of the ganglion arise from its anteri convex aspect, and are known as divisions. They are as follow the first or ophthalmic division; the second or maxillary divisio and the third or mandibular division. The ophthalmic and maxilla nerves are entirely sensory, but the mandibular nerve, being join by the motor root, is both sensory and motor.
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The first division of the trigeminal nerve, or the ophthalmic ner\ is the smallest of the three branches of the ganglion. It passes fc wards in the outer wall of the cavernous sinus, where it lies below t] fourth nerve. On approaching the superior orbital fissure it divid into branches in the following order from behind forwards: (i) nas ciliary (nasal), (2) lacrimal, and (3) frontal. All these three branch enter the orbit through the superior orbital fissure. As the ophthaln nerve passes forwards it receives a communicating branch from t' internal carotid sympathetic plexus, and it furnishes the nervus tento> to the tentorium cerebelli. It also communicates with each of t oculo-motor, trochlear, and abducent nerves.
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The naso-ciliary nerve, having passed through the orbit, re-ente the skull by running between the orbital plate of the frontal and t' upper surface of the ethmoid. It then lies deep to the dura mater < the cribriform plate near its anterior extremity, and soon disappea by passing down between this bone and the nasal area of the frontal
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The second division of the trigeminal nerve, or the maxillary ner (superior maxillary nerve), passes horizontally forwards for a she distance in the lower part of the outer wall of the cavernous sinus, ai it leaves the cranial cavity through the foramen rotundum, whi leads to the pterygo-palatine fossa. Before leaving the cranial cavi it furnishes the delicate meningeal nerve to the dura mater of tl middle fossa.
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The third division of the trigeminal nerve, or the mandibular ner (inferior maxillary nerve), is the largest of the three branches of t. ganglion. It passes downwards to the foramen ovale, through whi it leaves the cranial cavity, and so enters the infratemporal foss It is accompanied by the motor root of the fifth nerve, which joi it as it passes through the foramen ovale. The nervus spinosus fre the mandibular nerve is not given off until after the parent trui has issued through the foramen ovale, and it enters the cranial cavi through the foramen spinosum in company with the middle meninge artery. It then divides into two branches, anterior and posterior. T anterior branch supplies the dura mater over the greater wing of t sphenoid bone, and the posterior branch passes through the fissr between petrous and squamous parts of the temporal bone to supp the mucous membrane of the mastoid air-cells.
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Greater Superficial Petrosal Nerve. —This nerve is a branch of the gangli of the facial nerve in the facial canal. It enters the middle fossa of the be of the skull through its hiatus, and passes forwards and inwards in a groove
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THE HEAD AND NECK
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1169
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anterior surface of the petrous part of the temporal bone. Having passed sath the trigeminal ganglion embedded in the dura mater, it enters the upper of the foramen lacerum, where it is placed on the outer side of the internal tid artery, and it joins the deep petrosal nerve from the internal carotid pathetic plexus. In this manner the nerve of the pterygoid canal is formed,
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h enters the latter canal by its opening on the anterior aspect of the foramen
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rum, and so reaches the spheno-palatine ganglion in the pterygo-palatine i. The greater superficial petrosal nerve is accompanied by the superficial osal branch of the middle meningeal artery.
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jesser Superficial Petrosal Nerve. —This nerve represents the continuation ugh the tympanic plexus of the tympanic branch (Jacobson's nerve) of the 30-pharyngeal nerve. It is reinforced by a small branch from the ganglion he facial nerve, Avhich joins it as it traverses a small canal in the petrous of the temporal bone beneath the canal for the tensor tympani muscle, nerve enters the middle fossa through a small opening on the lateral side he hiatus for the greater superficial petrosal nerve. It then passes for a 3 forwards and inwards, and leaves the cranial cavity through the canaliculus iminatus (when present), or through the fissure between the petrous temporal the greater wing of the sphenoid, or, it may be, through the foramen ovale, r which it terminates in the otic ganglion.
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External Petrosal Nerve. —This nerve, which is inconstant, passes from the pathetic plexus on the middle meningeal artery backwards and outwards
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he anterior surface of the petrous part of the temporal bone, and it leaves
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cranial cavity through a minute aperture situated within the thin margin tie hiatus for the greater superficial petrosal nerve. It ends in the ganglion re facial nerve.
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Interior of the Cavernous Sinus.—The interior of this sinus ia ken up by a network of delicate trabeculae. The outer wall of sinus contains the following rial nerves, in order from above mwards: the oculo-motor, the ihlear, the ophthalmic division
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he trigeminal, and the maxilr division of the fifth. These
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ves, as they pass forwards, separated from the bloodrent by the endothelial lining the outer wall of the sinus.
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J cavity of the sinus is travel by (1) the cavernous portion the internal carotid artery, rounded by a plexus of symhetic filaments; and (2) the Lucent nerve, which lies in >e contact with the outer side of the artery. These structures are ) separated from the blood-current by the endothelial lining of the is.
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For the processes and other sinuses of the dura mater see p. 1601. Cavernous Portion of the Internal Carotid Artery.—This part of the irnal carotid artery lies within the cavernous sinus, which occupies carotid groove on the lateral aspect of the body of the sphenoid ie. It is separated from the blood-current by the endothelial
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74
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Internal Carotid Artery Abducent.Nerve Oculo-motor Nerve Trochlear Nerve Ophthalmic Nerve
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Sella Turcica
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Maxillary Nerve
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Left Sphenoidal Sinus
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Fig. 701.—Diagram of the Left Cavernous Venous Sinus and its Outer Wall, showing the Relative Positions of the Contained Structures (Posterior View).
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1170
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A MANUAL OF ANATOMY
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lining of the sinus. The course of the vessel is at first upwan between the lingula of sphenoid and the posterior petrosal process the sphenoid; then forwards as far as the anterior clinoid process the sphenoid; and finally upwards medial to the anterior clinc process. In the latter situation it pierces the dura mater, whi forms the roof of the cavernous sinus, and enters upon the cerebi part of its course.
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The vessel is accompanied by the internal carotid sympathe plexus, and the abducent nerve lies in close contact with its out side, all being invested by the endothelial lining of the sinus.
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Fig. 702.—Right Internal Carotid put in Position on Base of Skui
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and Crossed by Sixth Nerve.
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Great superficial petrosal nerve is also seen.
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Branches.—These are as follows: hypophysial, to the hypophys cerebri; ganglionic, to the trigeminal ganglion; cavernous, to the w£ of the cavernous sinus, and to the oculo-motor, trochlear, trigemim and abducent nerves; meningeal, to the dura mater of the midd cranial fossa; and the ophthalmic artery. The latter vessel arises fro: the cavernous portion of the internal carotid on the inner side of tl anterior clinoid process, and it enters the orbit, with the optic nerv through the optic foramen, lying at first beneath the nerve, and the on its outer side.
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The Medial Part of the Internal Carotid Sympathetic Plexus (Caveri ous Plexus).—This plexus is situated principally on the inner and low< aspects of the bend which the cavernous portion of the internal caroti
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THE HEAD AND NECK
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1171
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•y describes medial to the anterior clinoid process. Its branches as follows; (1) vascular, to the internal carotid artery and its ches; (2) hypophysial, to the hypophysis cerebri; (3) communing, to the oculo-motor, trochlear, ophthalmic division of the tri[nal, and abducent cranial nerves; and (4) the sympathetic root of
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iliary ganglion. The last-named branch enters the orbit through
 +
superior orbital fissure.
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"he hypophysis cerebri (pituitary body) is a small oval mass which tuated in the hypophysial fossa, or sella turcica, of the sphenoid It lies under cover of a circular fold of the dura mater, called the hragma sellce, in the centre of which is an opening for the passage le infundibulum. Its long measurement extends transversely, and msists of two lobes—anterior and posterior. The anterior lobe is larger of the two, and the posterior lobe is connected with the rior part of the tuber cinereum by means of the infundibulum, rhe infundibulum projects downwards from the anterior part of tuber cinereum to the posterior lobe of the pituitary body. Its sr part is hollow, and contains mnel-shaped diverticulum of the ty of the third ventricle.
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tructure. —The anterior lobe consists of ral tubules lined with epithelium, and sted by capillary bloodvessels. The jrior lobe, though developed from the 1, is destitute of nervous elements. It imposed of a reticulum of connective e, which contains branched cells. Bern the two lobes is the middle part.
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)evelopment. —The anterior lobe is deped from a diverticulum of the buccal tomatodaeal ectoderm, which is known ie pouch of Rathke. The diverticulum rs upwards, and, when the cranio•yngeal canal of early life becomes closed, connection of the diverticulum with the
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al ectoderm is severed. The diverurn later on becomes converted into
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lies, which form the anterior lobe, dhe Brior lobe of the pituitary body and the ndibulum, which is connected with it, are sloped as a diverticulum which grows nwards from that part of the diencephalon
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h forms the floor of the third ventricle. #
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cavity of the diverticulum remains permanent in the upper part of its ndibular portion, but elsewhere it becomes obliterated. The lower part of diverticulum thereafter becomes converted into a reticulum of connective ie with branched cells, which forms the posterior lobe.
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Fig. 703. —Diagram of Anteroposterior Section through the Hypophysis.
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A, anterior lobe: PT, its pars tuberalis. Pars Interm., pars intermedia. N, neural or posterior lobe. INF, infundibulum. OPT. CH, optic chiasma.
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Side of the Neck.
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The side of the neck has a quadrilateral outline, the boundaries which are as follows: superior, the lower border of the mandible . a line prolonged from the angle of that bone over the mastoid
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1172
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A MANUAL OF ANATOMY
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process to the inner third of the superior rruchal line of the occipi bone; inferior , the clavicle and one half of the upper border of 1 manubrium sterni; anterior , the middle line of the neck; and posteri the outer border of the trapezius in the neck.
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Landmarks.—The body and angle of the mandible can easily felt, and the clavicle, together with the upper border of the manubrii sterni, is conspicuous. A deep depression, called the supraster: fossa, is perceptible above the upper border of the manubrium ster lying between the sternal h'eads of origin of the sterno-mastoid muscl The outline of the sterno-mastoid muscle is readily discernible when 1 head is turned so as to direct the face towards the opposite should The muscle extends in a diagonal direction from the sterno-clavicu joint to the mastoid process and outer half or two-thirds of the super nuchal line of the occipital bone, and it divides the side of the ne into two triangles—anterior and posterior. A small triangular inter may be felt between the sternal and clavicular heads of origin of t sterno-mastoid just above the inner end of the clavicle, in which t common carotid artery and internal jugular vein lie deeply. T external jugular vein crosses the sterno-mastoid muscle in the directi of a line extending from a point just behind the angle of the mandil to a point above the centre of the clavicle, and it is accompanied the superficial cervical glands. The common carotid artery lies unc cover of the anterior border of the sterno-mastoid muscle in the directi of a line drawn from the sterno-clavicular joint to a point midw between the angle of the mandible and the tip of the mastoid proc( of the temporal bone. The vessel extends along this line as high the level of the upper border of the thyroid cartilage, above which is replaced by the external carotid artery. The internal jugular vt is close to the outer side of the common carotid artery, and the vag nerve lies deeply between the two vessels. If deep pressure is ma over the common carotid artery on a level with the cricoid cartila of the larynx, the anterior tubercle of the transverse process of t sixth cervical vertebra may be felt. It is known as the carotid tuber (of Chassaignac.)
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The bifurcation of the innominate artery lies behind the upp border of the right sterno-clavicular joint, and the left common carol artery lies behind the left sterno-clavicular joint, while the lower pa of the internal jugular vein on each side is behind the inner end the clavicle. Near the middle line of the neck the anterior jugul vein descends vertically. The spinal root of the accessory ner passes downwards and outwards beneath the anterior border of t sterno-mastoid to pierce the deep part of that muscle at about t junction of the upper fourth and lower three-fourths. The nerve met with fully 1 inch below the tip of the mastoid process, and in t direction of a line let fall vertically from the mastoid tip. It is ve nearly on a level with the body of the hyoid bone. Along the posteri border of the sterno-mastoid some superficial cervical lymph glan may be felt.
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THE HEAD AND NECK
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ii 73
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Important structures occupy the middle line of the neck, and can usually distinguished without difficulty. These are as follows, in sr from above downwards: (1) the body of the hyoid bone, lying
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below the mandible, and having the greater horn projecting
 +
kwards and upwards on either side; (2) the thyro-hyoid membrane; the thyroid cartilage, with its laryngeal prominence (pomum imi) in the middle line, leading up to the V-shaped thyroid notch the upper border, and its expanded ala on either side, each of which s behind in a superior and an inferior horn; (4) the crico-thyroid ment; (5) the narrow anterior part of the cricoid cartilage, which icides with the level at which the superior belly of the omo-hyoid
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scle crosses the carotid sheath; and (6) the rings of the trachea, ich, however, are covered superiorly by the isthmus of the thyroid nd, and inferiorly by the sterno-hyoid and sterno-thyroid muscles 1 adipose tissue.
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The lateral lobes of the thyroid gland may be felt on either side of larynx and trachea as low as about the fifth ring; and in young Idren the thymus extends upwards upon the trachea for some tance above the manubrium sterni.
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The greater horn of the hyoid bone is the guide to the lingual artery , hypoglossal nerve for operative purposes, the structures lying just ve the greater horn.
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A MANUAL OF ANATOMY
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1174
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The upper border of the thyroid cartilage is on a level with the di between the bodies of the third and fourth cervical vertebra.
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The narrow anterior part of the cricoid cartilage is on a level wi the disc between the bodies of the fifth and sixth cervical vertebrae, which level the pharynx becomes the oesophagus. In this situatior foreign body, when swallowed, is liable to become impacted.
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Below the cricoid, in the middle line, one or two rings of the trach may be felt above the thyroid isthmus, and it is here that a hi tracheotomy is performed, an easy operation since the windpipe is
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Fig. 705. —Superficial Dissection.
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close to the skin. Below the isthmus the trachea rapidly recedes, that a low tracheotomy is often a difficult and sometimes a ve dangerous operation; dangerous because, often in children and son times in the adult, the left innominate vein lies in the suprasterr region above the level of the manubrium sterni, and so in the way the knife. Ignorance of this fact has meant, and may mean aga the loss of a life.
 +
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Above the middle third of the clavicle, between the sterno-mash and trapezius muscles, there is a depression known as the greai
 +
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THE HEAD AND NECK
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ii 75
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aclavicular fossa, which indicates the position of the subclavian lgle, with the third part of the subclavian artery and the trunks ie brachial plexus of nerves.
 +
 +
Platysma (Platysma Myoides)— Origin .—The superficial fascia which >rs the clavicular parts of the pectoralis major and deltoid muscles. Insertion. —(1) The outer part of the body of the mandible from symphysis menti to the anterior border of the masseter muscle; (2) the angle of the mouth, where the fibres blend with those of depressor anguli oris and orbicularis oris.
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Nerve-supply .—The cervical branch of the facial nerve, which comlicates with branches of the anterior cutaneous nerve of the neck. The fibres are directed upwards and forwards or inwards over the dele and side of the neck.
 +
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Action. —(1) To draw the angle of the mouth downwards and outds; (2) to act as a feeble depressor of the mandible; (3) to raise the 1 of the neck and upper pectoral region as far out as the acromion cess, throwing it into obliquely-disposed folds.
 +
 +
The muscle forms an extensive, thin, pale sheet, which is embedded hin the superficial fascia. In the region of the symphysis menti innermost fibres decussate across the middle line with those of the >osite side, the fibres of the right muscle being superficial. The scle covers the external and anterior jugular veins, the superficial nches of the cervical plexus of nerves, the subclavian triangle, and sterno-mastoid, sterno-hyoid, omo-hyoid, and digastric muscles.
 +
 +
The platysma in man is a remnant of a subcutaneous muscular sheet, called panniculus carnosus, which exists in many animals, and by which the twitchof the skin is produced.
 +
 +
Jugular Veins.—The jugular veins are four in number on either e—anterior, external, posterior external, and internal.
 +
 +
The anterior jugular vein begins in the roof of the digastric triangle, Lere it is formed by the union of radicles which communicate with 3 submental vein, and are joined by radicles which have descended >m the structures over the body of the mandible. It descends rtically near the median line, lying at first superficial to the deep rvical fascia, but subsequently entering the suprasternal space. II en describes a bend, and, passing outwards behind the sternoistoid muscle, and in front of the scalenus anterior, it opens to the lower part of the external jugular vein. It may, however, >en into the subclavian vein. It communicates with the external gular vein by one or more tributaries, and usually receives a branch 3 m the facial vein which descends along the anterior border of the erno-mastoid and joins it towards the lower part of the neck, urther, it communicates with its fellow, of the opposite side by a ansverse branch, the jugular arch, which crosses in front of the achea, and lies in the suprasternal space.
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 +
The anterior jugular veins are usually asymmetrical, one or other sing of small size. Occasionally there is only one vein, which divides
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A MANUAL OF ANATOMY
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1176
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into two vessels interiorly. The anterior jugular vein is destitute ^ valves.
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The external jugular vein commences close behind the angle of tl mandible in the substance of the parotid gland, where it is formed t the union between the posterior division of the posterior facial ve: and the posterior auricular vein. On leaving the parotid gland descends almost vertically to a point above the centre of the clavicl In its course the vessel crosses the sterno-mastoid muscle, lying supe ficial to its sheath, and deep to the superficial fascia containing tl fibres of the platysma. At this level the main part of the anteri<
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Fig. 706. —Superficial Veins of Neck.
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SF, CF, superficial and common facial. TM, posterior facial or temporo-maxillar PA, posterior auricular. PJ, EJ, AJ, posterior, external, and anterior juguls
 +
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cutaneous nerve of -the neck runs forward deep to the vein, and offse of the nerve pass superficial to it. Having crossed the sterno-masto muscle, the vein descends not far from its posterior border, where lies in the roof of the subclavian triangle over the third part of tl subclavian artery. Up to this point the vessel is superficial to tl deep cervical fascia, but it now pierces that fascia and opens into tl subclavian vein.
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The course of the external jugular vein is indicated by a line draw from a point close behind the angle of the mandible to a point abo^ the centre of the clavicle. Its tributaries are as follows: (1) poster!
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THE HEAD AND NECK
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1177
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3rnal jugular, which joins it about the middle of the neck; (2) trans;e cervical; (3) suprascapular; and (4) anterior jugular, the latter
 +
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e joining it not far from its termination. It also communicates
 +
1 the anterior jugular vein by one or more branches. The vessel rovided with valves, both at its termination and about i\ inches ve this point, and the transverse cervical and suprascapular veins
 +
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isterior Auricular Lymph Glands
 +
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Occipital Vein
 +
 +
al Lymph Gland
 +
>r Auricular Vein
 +
 +
terior Division of
 +
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erior Facial Vein
 +
iperficial Cervical Lymph Glands
 +
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osterior External Jugular Vein
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mal J ugular Vein
 +
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rse Cervical Vein_
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P, ,
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whi 1 \n\
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_Supratrochlear Vein
 +
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-Supra-orbital Vein
 +
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- Angular Vein
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Superficial Temporal Vein Maxillary Vein
 +
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Posterior Facial Vein Anterior Facial Vein
 +
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Ant. Div. of Posterior Facial Vein
 +
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Submandibular Lymph Glands
 +
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Common Facial Vein Internal J ugular Vein Lingual Vein
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Superior Thyroid Vein
 +
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Middle Thyroid Vein
 +
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Anterior Jugular Vein
 +
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. Suprasternal Lymph Gland
 +
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. 1 ■"
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Suprascapular Vein and.Supraclavicular; Lymphatic Glands
 +
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r. 707. —The Superficial Veins and Superficial Lymph Glands of the
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Right Side of the Head and Neck.
 +
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The platysma muscle has been removed.
 +
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 +
i also furnished with valves where they open into the external
 +
 +
ular vein, or near their orifices.
 +
The external jugular vein is sometimes very small, or even absent, I it may communicate with the cephalic vein by a vessel which sses over the clavicle.
 +
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r
 +
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Development. —The external jugular vein was formerly regarded as being sloped from the anterior cardinal vein; but according to most authorities anterior cardinal vein gives rise to the internal jugular vein, the external ular being of later development.
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A MANUAL OF ANATOMY
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1178
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The posterior external jugular vein represents the most exter: occipital vein, and is formed by tributaries which issue from the ou part of the occipital plexus, reinforced by veins from the superfic structures at the back of the neck. It usually receives the mast' emissary vein and passes downwards and forwards, joining the exter: jugular vein about the middle of the neck.
 +
 +
The internal jugular vein will be found described on p. 1211.
 +
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Superficial Cervical Lymph Glands.— These are about six in numb and they lie upon the sterno-mastoid muscle, along the course of 1 external jugular vein, and deep to the superficial fascia and platysi muscle. They receive their afferent lymphatics from the adjac< superficial structures, the occipital and mastoid lymph glands, a some of those of the parotid and submandibular lymph glands. Tb efferent lymphatics pass to the deep cervical lymph glands.
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Deep Cervical Fascia. —The deep cervical fascia is divided ii (1) a superficial investing layer, which completely invests the neck the form of a collar; and (2) deep processes or laminae, which inv the muscles, viscera, and chief bloodvessels and nerves.
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Investing Layer. —This layer is attached posteriorly to the li\ mentum nuchae; superiorly to (1) the superior nuchal line of the oc pital bone, (2) the mastoid process of the temporal bone, (3) the zyj matic arch, and (4) the body of the mandible, under cover of 1 platysma, as far forwards as the symphysis menti; and interiorly the clavicle and upper border of the manubrium sterni, being pierc above the centre of the clavicle by the external jugular vein. Ale the middle line of the neck anteriorly it is continuous with the invest] layer of the opposite side.
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The investing layer invests the cervical portion of the trapezi and from the anterior border of that muscle it passes forwards 0 1 the posterior triangle of the neck to the posterior border of the sten mastoid. In doing so it furnishes a deep process, which ensheat] the inferior belly of the omo-hyoid muscle. This process also embra^ the intermediate tendon of that muscle, after which it passes dov wards and inwards to be attached to the back of the inner end of 1 clavicle and the first rib. In this manner the horizontal position the inferior belly of the omo-hyoid is accounted for. When the vesting layer of the deep cervical fascia reaches the posterior bore of the sterno-mastoid it splits into two laminae, which ensheathe tl muscle, the superficial lamina being underneath the external jugu vein and platysma. At the anterior border of the sterno-mastoid 1 two laminae reunite, and the fascia passes forwards over the anter triangle of the neck to the median line, where it is continuous with 1 corresponding layer of the opposite side.
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Between the upper part of the anterior border of the sterno-masb and the angle of the mandible the investing layer is of considera strength, and draws that border of the muscle forwards and upwar so as to render it convex and keep it over the line of the leading vess< Between the mastoid process and the angle of the mandible the
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THE HEAD AND NECK
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1179
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ting layer is prolonged upwards over the parotid gland as the parotid
 +
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ia, which is very dense, and is attached superiorly to the lower
 +
der of the zygomatic arch.
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 +
Below the level of the thyroid gland the investing layer divides 0 two laminae, anterior and posterior, both of which are superficial the infrahyoid muscles. At the middle line these laminae are conuous with those of the opposite side, and inferiorly they are attached the anterior and posterior margins of the upper border of the nubrium sterni. Between them there is an interfascial interval, led the suprasternal space (space of Burns). This interval contains
 +
 +
olar tissue, one or more lymphatic glands, the lower portions of the
 +
terior jugular veins, with the jugular arch which here connects im, and the sternal heads of the sterno-mastoid muscles.
 +
 +
Deep Processes or Laminae.— The deep laminae, as stated, invest the iscles, viscera, and chief bloodvessels and nerves. The most imrtant are derived from that lamina of the investing layer which ms the posterior wall of the sheath of the sterno-mastoid muscle, d they are three in number—namely, carotid sheath, pretracheal icia, and prevertebral fascia—all of which have an intimate initial nnection.
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The carotid sheath contains in separate compartments (1) the mmon carotid artery and the constituents of the ansa hypoglossi, the internal jugular vein, and (3) the vagus nerve, the latter being ntained within the back part of the septum, which separates the tery from the vein.
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The pretracheal fascia, which is at first intimately connected with e anterior wall of the carotid sheath, passes forwards behind the frahyoid muscles, in which situation it splits to ensheathe the yroid gland, trachea, and oesophagus, and then it passes to the sdian line, where it is continuous with the pretracheal fascia of the •posite side. The pretracheal fascia is attached superiorly to the >dy of the hyoid bone, and inferiorly it descends over the trachea Ld bloodvessels into the superior mediastinum of the thorax, where it ends with the fibrous pericardium.
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The prevertebral fascia, which is at first intimately connected with e posterior wall of the carotid sheath, passes forwards behind the larynx and oesophagus, and in front of the prevertebral muscles, t the middle line it is continuous with the corresponding fascia of e opposite side; superiorly it is attached to the base of the skull; id inferiorly it descends over the longus cervicis muscle into the isterior mediastinum of the thorax. Along a line corresponding to le inner wall of the carotid sheath the pretracheal fascia furnishes a condary lamina, called the bucco-pharyngeal fascia, which covers ie constrictor muscles of the pharynx and the buccinator muscle, etween the bucco-pharyngeal and prevertebral fasciae there is an terval, called the retro-pharyngeal space, which contains the loosely 'ranged connective tissue uniting the two fasciae. This space extends high as the base of the skull, and inferiorly is continuous with the
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ii8o
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A MANUAL OF ANATOMY
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posterior mediastinum of the thorax. Another process of the pi vertebral fascia passes downwards and outwards in front of t scalenus anterior muscle. After this it invests the third part of t subclavian artery and subclavian vein, together with the nerve-trun of the brachial plexus, and, passing behind the clavicle, it becom continuous with the axillary sheath, which latter blends with t posterior aspect of the clavi-pectoral fascia. In the region of the su clavian triangle there is an interfascial space between this proce of the pretracheal fascia and the investing layer of the deep cervic fascia. This space extends downwards behind the clavicle to the poi where the axillary sheath and clavi-pectoral fascia join. It contai
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Stemo- thyroid Sterno-hyoid
 +
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Investing Layer of Deep Cervical Fascia Superior Belly of Omo-hyoid Pretracheal Fascia Prevertebral Fascia
 +
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Suprasternal Space Trachea
 +
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Muscular Compartment
 +
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Lateral Lobe of Thyroid Gland
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Carotid Sheath
 +
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Scalenus Anterior
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Scalenus Medius
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Levator Scapulae
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Semispinalis Capitis
 +
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(Esophagus
 +
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Descendens hypoglossi ^ Common Carotid Artery Internal Jugular Vein - Vagus Nerve Platysma
 +
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Splenius
 +
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Sympathetic Trunk
 +
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Longus Cervicis - Stemo-mastoid
 +
 +
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External Jugular V<
 +
 +
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' Vertebral Vessels
 +
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Trapezius
 +
 +
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Semispinalis Cervicis
 +
 +
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Tig. 708. Diagram of a Transverse Section of the Neck at the Lev of the Sixth Cervical Vertebra, showing the Arrangement of ti Deep Cervical Fascia and the Positions of Other Structures.
 +
 +
 +
the inferior belly of the omo-hyoid muscle, the suprascapular ar transverse cervical vessels, the lower part of the external jugular vei and the terminal portion of the anterior jugular vein.
 +
 +
Interfascial Compartments. —It has been stated that the det cervical fascia reaches the median line of the neck anteriorly in thr layers—namely, investing (in two divisions), pretracheal, and pr vertebral. It is therefore evident that there are four interfasci compartments as follows: (1) the suprasternal space (space of Burn! which is situated between the two divisions of the investing layer, ai contains the structures already enumerated; (2) the muscular cor partment, which is situated between the investing layer and the pr tracheal layer, and contains the infrahyoid muscles; (3) the viscer
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THE HEAD AND NECK
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1181
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partment, which lies between the pretracheal and prevertebra rs, and contains the larynx, trachea, thyroid gland, pharynx, phagus, and carotid sheath, the retro-pharyngeal space being in subdivision of this compartment behind the bucco-pharyngeal ia; and (4) the vertebral compartment, which lies between the vertebral layer and the attachment of the fascia to the ligamentum iae posteriorly, and contains the vertebral column, spinal cord, and vertebral and postvertebral muscles.
 +
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rhe suprasternal and muscular compartments are shut off from thoracic cavity. The visceral compartment in front of the trachea mtinuous with the superior mediastinum of the thorax, and behind oesophagus it, along with the retro-pharyngeal space, is continuous 1 the posterior mediastinum.
 +
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Parotid Process of the Deep Cervical Fascia. —This process is given a little below the angle of the mandible, and it passes upwards on deep surface of the parotid gland to the skull. Along with the Dtid fascia superficial to the gland it forms a dense sheath which ely invests the glandular substance. The parotid process furnishes aths to the posterior belly of the digastric, styloid, and pterygoid scles, and it also gives an investment to the superficial part of the mandibular gland. Connected with the parotid process there are sral bands, usually called ligaments, which are as follows: (1) sphenoadibular; (2) stylo-mandibular; (3) pterygo-mandibular; and
 +
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pterygo-spinous.
 +
 +
The spheno-mandibular ligament will be described in connection h the mandibular joint, of which it is sometimes regarded as an essory medial ligament (see p. 1316).
 +
 +
The stylo-mandibular ligament extends from the styloid process of temporal bone near its tip to the angle and adjacent part of the terior border of the ramus of the mandible, where it is placed ween the masseter and internal pterygoid muscles.
 +
 +
The pterygo-mandibular ligament is a narrow band which extends hi the hamulus of the medial pterygoid plate of the sphenoid bone the posterior extremity of the mylo-hyoid line of the mandible $e to the last molar socket. Anteriorly it gives origin to fibres of buccinator muscle, and posteriorly to fibres of the superior condor muscle of the pharynx.
 +
 +
The pterygo-spinous ligament is a narrow band which extends from harp spine on the posterior border of the lateral pterygoid plate of sphenoid bone, towards its upper part, to the spine process of the lenoid. This ligament is liable to become ossified.
 +
 +
The foregoing description is orthodox and traditional, and every fact stated be demonstrated by a good dissector; but there are some observers who 3rd the whole of these fascial planes as artifacts, and believe that all the irstices between the structures in the neck are filled with loose connective ue which, when it is cleaned from the surrounding parts, collapses into Y definite sheets. If this is the case, it should be possible, by varying the action of the incisions, to produce sheets in any plane. As a matter of fact, > can be done.
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Il82
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A MANUAL OF ANATOMY
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Sterno-mastoid — Origin .—The sternal head, which is narrow ar round, arises from the upper and outer part of the anterior surfa* of the manubrium sterni. It is tendinous in front, and fleshy behin The clavicular head, which is broad and flat, arises from a rough rid| about ij inches long on the upper surface of the clavicle at its inn end.
 +
 +
Insertion .—The outer surface of the mastoid process of the ter poral bone, and the superior nuchal line of the occipital bone ov about its outer half or two-thirds.
 +
 +
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Fig. 709. —Showing Sterno-mastoid and the Muscular Floor of
 +
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Posterior Triangle.
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Nerve-supply .—The accessory nerve, and a branch from the cervic plexus, more particularly from the anterior primary ramus of the secor cervical nerve.
 +
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The spinal root of the accessory nerve passes deep to the anteri border of the muscle fully 1 inch below the tip of the mastoid proces and in passing downwards and backwards it pierces the deep part the muscle, giving off as it does so its branches to it.
 +
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The muscle is directed upwards, outwards, and backwards.
 +
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Action .—To flex the head towards the side on which the muse
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THE HEAD AND NECK
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1183
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aced, the face being turned towards the opposite side. This is position of the head in torticollis or wry-neck, a condition which be due to an organic contraction to the muscle, affecting both s, or, it may be, the sternal head alone. When both muscles act ther from their origin they flex the head towards the thorax, when the head has been already thrown back the sterno-mastoid ls capable of extending it still farther instead of flexing it. It t be remembered, however, that a certain amount of flexion of lead may take place between any of the cervical vertebrae. When muscles act together from their insertion they elevate the upper of the anterior thoracic wall in forced inspiration.
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"he sternal and clavicular heads are separated by a triangular Jar interval for a short distance above the sterno-clavicular joint, before their junction the fibres of the clavicular head to a large nt pass behind those of the sternal head, so that overlapping s place. The muscle is surrounded by a strong sheath, which is led by the deep cervical fascia. The platysma covers a large part
 +
 +
, and the external jugular vein, the anterior cutaneous nerve of
 +
and great auricular nerves, and the superficial cervical lymph
 +
ds are related to its superficial surface under cover of the platysma. principal deep relations are as follows: in the lower part of the
 +
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it covers the first and second parts of the subclavian artery, the
 +
10-hyoid, sterno-thyroid, omo-hyoid, and scalenus anterior muscles, l the phrenic nerve lying upon the last-named muscle. In this rtion it also covers the anterior jugular vein, and the transverse ical and suprascapular arteries. Higher up it covers the cervical
 +
 +
us of nerves, the levator, scapulae, scalenus medius, and scalenus
 +
erior muscles, and the accessory and the hypoglossal nerves. At insertion it covers the splenius capitis, longissimus capitis, and
 +
 +
erior belly of the digastric muscles, and a portion of the occipital
 +
ry, in this order from the surface downwards. The anterior border he muscle forms the posterior boundary of the anterior triangle of neck, and covers the carotid sheath, with its contents, as high as level of the upper border of the thyroid cartilage ; and above that 1 it covers the external and internal carotid arteries. This border overlaps slightly the lateral lobe of the thyroid gland.. The
 +
 +
erior border forms the anterior boundary of the posterior triangle
 +
he neck, and along it there lie the following structures: the superI cervical lymph glands, the lesser occipital nerve, great auricular, nrior cutaneous nerve of neck, the accessory, and the descending srficial branches of the cervical plexus of nerves, and a portion of external jugular vein.
 +
 +
The sterno-mastoid muscle, from its diagonal position upon the
 +
 +
of the neck, divides the quadrilateral space into two triangles terior and anterior.
 +
Posterior Triangle. —This is the region which lies behind the sterno>toid muscle.
 +
 +
Boundaries — Anterior. —The posterior border of the sterno-mastoid.
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A MANUAL OF ANATOMY
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1184
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Posterior .—The anterior border of the trapezius. Inferior (base).— middle third of the clavicle. The apex is at the superior nuchal of the occipital bone, where the sterno-mastoid and trapezius may n but the apex is usually truncated. The roof is formed by the ; superficial and deep fasciae, and for a short distance interiorly by platysma. The lesser occipital nerve lies in the upper part of roof, and the descending superficial branches of the cervical pi and the external jugular vein lie in the lower part of the roof, floor is formed by the following muscles, in order from above dc wards: (1) small angle of the semispinalis capitis, provided the trapt
 +
 +
 +
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is not well developed at the occiput; (2) the splenius capitis; (3) levator scapulae; (4) the scalenus medius and scalenus poster (5) the scalenus anterior; and (6) the first digitation of the sern anterior if the clavicle is depressed.
 +
 +
The posterior triangle is subdivided by the inferior belly of omo-hyoid into a large upper portion, called the occipital trian and a small lower portion, called the subclavian triangle.
 +
 +
Occipital Triangle—Boundaries — Anterior .—The posterior boi of the sterno-mastoid. Posterior .—The anterior border of trapezius. Inferior (base). —The inferior belly of the omo-hy The muscles in its floor are (1) a small angle of the semispinalis caj
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THE HEAD AND NECK
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1185
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instant), (2) splenius capitis, (3) levator scapulae, and (4) scalenus .ius and posterior. The contents are the superficial branches of the ical plexus, the accessory nerve, the branches of the cervical
 +
 +
us to the levator scapulae and trapezius, a small part of the occipital
 +
ry close to the apex, and some superficial cervical lymph glands.
 +
 +
t should be realized that the foregoing gives a picture of the triangle as seen le dissected body. In life and in the undissected part it is little more than tter, the anterior edge of the trapezius being only about \ inch from the srior border of the sterno-mastoid.
 +
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Parotid Duct Buccinator Muscle
 +
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Facial Artery Submental Artery
 +
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Lingual Artery Sup. Lar. Art. and Nerve Thyro-hyoid Muscle Superior Thyroid Artery
 +
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.Transverse Facial Artery
 +
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, Superficial Temporal Artery
 +
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- Maxillary Artery
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/_Posterior Auriculat
 +
 +
wma ^ . Artery
 +
 +
Occipital Artery
 +
 +
 +
-Stylo-hyoid Muscle
 +
 +
-Post. Belly of Digastric
 +
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-Hypoglossal Nerve
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_Descendens Hypogloss'
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_External Carotid
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Artery
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-Sterno-mastoid
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.— w Trapezius
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_Transverse Cervical Artery
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-. Suprascapular Artery
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Inf. Belly of Omo-hyoid
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Subclavian Artery (third part)
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, y 1, An
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Fig. 711.—The Left Side of the Head and Neck. The platysma has been removed.
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Cervical Plexus. —The cervical plexus lies deep to the upper part
 +
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he sterno-mastoid muscle, and immediately in front of the slips
 +
•rigin of the scalenus medius. It is formed by the anterior primary ii of the first three cervical nerves and the greater part of that of fourth, a small branch of the latter descending to join the anterior nary ramus of the fifth, and so taking part in the brachial plexus, h of the anterior primary rami of the first four cervical nerves is nected with the superior cervical ganglion of the sympathetic by 'ey ramus communicans.
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75
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1186 A MANUAL OF ANATOMY
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The anterior primary ramus of the first cervical nerve lies at f in the vertebrarterial groove of the atlas below the vertebral arte It then passes forwards in a groove on the outer surface of the supei articular process of the atlas, having the vertebral artery on its or side. It next emerges between the rectus capitis lateralis mu; (to which it gives a branch) and the rectus capitis anterior, ; descends in front of the root of the lateral mass of the atlas to join ascending branch of the second nerve. From the loop so forr
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Vagus
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Lesser Occip. N.
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N.toTh
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Int. La
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Ne
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Accessory Nerve ..
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Ext. Li Nerv
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Descent Hvpog Desc. C
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Ansa
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Ant. Jv
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Fig. 712.—Deep Relations of Sterno-mastoid, showing Cervical
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Plexus, etc.
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branches are given to the rectus capitis anterior and the longus cap muscles, and one or more branches pass to the hypoglossal nerve, destination of their fibres being the ramus descendens cervicalis 2 the nerves to thyro-hyoid and genio-hyoid.
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The anterior primary rami of the second, third, and fourth cervi nerves, having emerged between the corresponding intertransversa muscles, form a superficial and a deep part of the plexus, of wh the superficial is altogether cutaneous, while the deep is divided h
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Phrenic
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Upper Cord of Brachial Plexus
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THE HEAD AND NECK
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1187
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tor and communicating branches. It will also be found that the p plexus consists of an external and an internal set of branches. Superficial Group. —The branches of this group are ascending, nsverse, and descending.
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The ascending and transverse branches arise from the second and
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d cervical nerves.
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The ascending nerves are the lesser occipital and great auricular
 +
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p. 1141). The transverse branch is the anterior cutaneous nerve
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he neck.
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The anterior cutaneous nerve of the neck (superficial cervical nerve)
 +
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es by two roots from the anterior primary rami of the second and
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Fig. 713. —Scheme of Cervical Plexus. superficial plexus red ; deep plexus black. I., E., medial and^lateral sides.
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'rd cervical nerves, and, turning round the posterior border of the Tno-mastoid muscle, it passes forwards superficial to that muscle, ng deep to the platysma and the external jugular vein. Having iched the anterior triangle of the neck, it divides into two branches,
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ending and descending, which are distributed to the integument
 +
er the anterior triangle. The offsets of the ascending branch commicate freely with the cervical branch of the facial nerve deep to the itysma.
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The descending branches are the medial, intermediate, and lateral 3 raclavicular nerves, and they arise in common from the third and irth cervical nerves. As they descend they form distinct nerves,
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n88
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A MANUAL OF ANATOMY
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which lie on the roof of the subclavian triangle under cover of t platysma. For their distribution see p. 412.
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Deep Group. —The nerves of this group are arranged in two sets external and internal.
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External Set .—These nerves are muscular. The second ner furnishes a branch to the sterno-mastoid, which communicates in tb muscle with the branch of the accessory nerve. The third and four
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Fig. 714. —Superficial Branches of Cervical Plexus.
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SO, lesser occipital; GA, greater auricular; TC, anterior cutaneous; DC, descending supraclavicular; XI, accessory nerve.
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nerves furnish (a) two branches to the trapezius, which communicc with the accessory nerve deep to the upper part of the muscle formi the subtrapezial plexus; ( b) two branches to the levator scapulae; a (c) branches to the scalenus medius.
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Internal Set .—The nerves of this set are communicating a muscular.
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The communicating branches are as follows: (1) connecting brand (grey rami communicantes) pass from the superior cervical gangli
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THE HEAD AND NECK
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1189
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the sympathetic; (2) communicating branches pass to the vagus d hypoglossal nerves from the highest loop of the plexus; and two rami communicantes cervicales pass from the second and third rves forwards and downwards, usually superficial, but sometimes ep to the internal jugular vein, and join the descendens hypoglossi, aether or separately, to form the ansa hypoglossi.
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The muscular branches are distributed to the rectus capitis lateralis,
 +
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tus capitis anterior and longus capitis, upper part of the scalenus
 +
terior, longus cervicis, and the diaphragm. The nerve to the iphragm is the phrenic, which, from its importance, requires a special scription.
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The phrenic nerve arises, as a rule, by two roots, the larger of lich is derived from the anterior primary ramus of the fourth cervical rve, and the other from that of the third. In some cases the fifth rvical nerve, which enters into the brachial plexus, furnishes an ditional small root. In the neck the nerve descends in front of the ilenus anterior muscle, which it crosses obliquely downwards and wards, passing deep to the intermediate tendon of the omo-hyoid uscle, the transverse cervical and suprascapular arteries, the anterior gular vein, and, on the left side, the thoracic duct. At the root of e neck the nerve, having left the scalenus anterior, passes behind e terminal part of the subclavian vein, and crosses in front of the ternal mammary artery from without inwards. Having come into ntact with the inner surface of the cupola of the pleura, it disappears kind the inner end of the clavicle, and enters upon the thoracic part its course (see p. 1015).
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The right nerve at the root of the neck is superficial to the second irt of the right subclavian artery, with the intervention of the alenus anterior muscle. The left nerve at the root of the neck is iterior and parallel to the first part of the left subclavian artery.
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The phrenic nerve is sometimes reinforced towards the root of the ick by a branch from the nerve to the subclavius muscle, and when is takes place the root from the fifth cervical nerve is usually absent, efore leaving the neck the phrenic nerve receives a twig from the iddle or inferior cervical ganglion of the sympathetic.
 +
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No branches arise from the phrenic nerve in the neck.
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Lower Group of Deep Cervical Lymph Glands (Supraclavicular pmph Glands). —These glands lie in the anterior part of the subclavian iangle, and are related superficially to the intermediate supraclavicular 'rve and deeply to the upper and middle trunks of the brachial plexus. 'iperiorly they are continuous with the upper deep cervical lymph ands. They receive their afferent vessels from the following sources:
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1. The back of the neck.
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2. The axillary lymph glands.
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3. The upper part of the pectoral region.
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4. Occasionally the lymphatics along the cephalic vein, which ay ascend over the clavicle.
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5- The internal mammary lymph glands.
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1190
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A MANUAL OF ANATOMY
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Their efferent vessels form the subclavian trunk, which, with t jugular trunk, opens into the thoracic, or into the right lymphai duct.
 +
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Subclavian or Supraclavicular Triangle. —The subclavian triangle the lower division of the posterior triangle of the neck, and is separate from the upper division or occipital triangle by the inferior belly
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Fig. 715. —Common Carotid and Subclavian Arteries exposed by Remow of Sterno-mastoid, Omo-hyoid, and Internal Jugular Vein.
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the omo-hyoid muscle. Situated above the middle third of the clavicl* it is of small size until the deep cervical fascia, which ensheathes tt inferior belly of the omo-hyoid, has been divided.
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Boundaries — Superior .—The inferior belly of the omo-hyoid muscf Inferior .—The middle third of the clavicle. Anterior .—The clavicuk part of the sterno-mastoid muscle. Roof .—The skin; superficial fasci
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THE HEAD AND NECK
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1191
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platysma muscle; medial, intermediate, and lateral supraclavicular es; a part of the external jugular vein; and the deep cervical fascia, if.—The scalenus medius and posterior muscles, and the serratus
 +
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rior.
 +
rhe extent of the triangle is affected by (T) the height to which inferior belly of the omo-hyoid ascends above the clavicle, and the extent of the clavicular attachments of the sterno-mastoid trapezius muscles. The depth of the triangle is influenced by the tion of the shoulder, being greater when the shoulder is raised carried forwards, and less when it is depressed and carried kwards.
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Contents. —The contents are: (1) the greater portion of the third t of the subclavian artery; (2) small portions of the transverse
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Brachial Plexus Cephalic Vein Musculo-cutaneous Nerve Deltoid
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Trapezius
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1 Suprascapular Vessels
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\ Transverse Cervical Artery
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Inferior Belly of Omo-hyoid
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Scalenus Anterior / Sterno-mastoid
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-Clavicle in section
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Subclavius
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Axillary Artery - Axillary Vein
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Pectoralis Major (cut)
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Pec!oralis Minor Lateral Root of Median Nerve
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Medial Cutaneous Nerve of Arm
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Axillary Vein
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Ulnar Nerve
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Medial Root of Median Nerve Medial Cutaneous Nerve of Forearm
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Fig. 716. —Subclavian and Axillary Regions.
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vical artery and vein; (3) the lower portion of the external jugular in; (4) the nerve-trunks of the brachial plexus; and (5) the nerve the subclavius muscle, the suprascapular nerve, and the nerve serratus anterior
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Third Part of the Subclavian Artery. —1 his part of the vessel extends >m the outer border of the scalenus anterior muscle to the outer rder of the first rib, where it becomes the axillaiy artery. Its course downwards and outwards, and for the greater part of its extent it s in the subclavian triangle. Its last inch or so, howevei, passes
 +
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hind the clavicle and subclavius muscle.
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Relations- — Anterior .—The skin; superficial fascia and platysma; edial, intermediate, and lateral supraclavicular nerves; deep cervical >cia; clavicle and subclavius muscle; transverse cervical vessels; prascapular vessels; nerve to the subclavius muscle; and the termina
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1192
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A MANUAL OF ANATOMY
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portion of the external jugular vein. The last-named vessel cro: in front of the artery close to the sterno-mastoid muscle, and in ■ situation is joined by the transverse cervical and suprascapular ve A plexiform arrangement of veins is sometimes met with in from the artery, which may be rendered more complex by a branch ascenc superficial to the clavicle from the cephalic vein. Posterior .—' scalenus medius, the lower nerve-trunk of the brachial plexus in vening. Superior .—The upper and middle nerve-trunks of the brad plexus, the latter being nearest the vessel. Inferior .—The upper s face of the first rib and the subclavian vein, the vein being on a m anterior plane than the artery, and lying behind the clavicle.
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It is most important to understand that, though the first rib is spoken o an inferior relation, its surface is so oblique that it is just as much behinc below.
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The third part of the subclavian artery does not always give any branch. In very many cases, however, the deep branch of transverse cervical artery arises from it, instead of from the latter arte
 +
 +
which is a branch of the first, p of the subclavian. In these ca the posterior scapular art passes outwards between nerve - trunks of the brad plexus.
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The direction of the third p of the artery is indicated b^ line drawn from a point on i posterior border of the ster mastoid muscle, about J ir above the clavicle, to the cen of that bone. The artery may compressed as it passes over 1 first rib, the guide to it at t point being the centre of i clavicle. In order to tie the si clavian artery in the dead bo< after fully depressing the clavi( feel for the outer edge of the scalenus anterior muscle, and follow to its insertion on the first rib. The structure which lies immediat behind the muscle here is the artery; and great care must be taken i to mistake it for the lower trunk of the brachial plexus.
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 +
For the manner in which the collateral circulation is carried after ligation of the third part of the subclavian artery, see p. 441.
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The subclavian vein, in the region of the subclavian triangle, situated behind the clavicle, where it lies below and anterior to 1 artery. On the upper surface of the first rib it is anterior to the scaler anterior, and it receives the external jugular vein, and in some ca the anterior jugular vein,
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Fig. 717.— Plan of Branches of Subclavian Artery.
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THE HEAD AND NECK
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ii 93
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L'he transverse cervical artery lies in the subclavian triangle for Lort distance only, close to where the inferior belly of the omoid passes deep to the sterno-mastoid. It passes outwards behind former muscle into the lower part of the occipital triangle, where ivides into its superficial and deep branches, the former entering trapezius, and the latter passing in front of the levator scapulae, r which it descends along the base of the scapula in front of the nboid muscles.
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rhe transverse cervical vein opens into the external jugular vein, •e being a valve at or near its ending.
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rhe suprascapular artery is not in the subclavian triangle, but lies ind the clavicle, close to its upper aspect. It will be described in nection with the first part of the subclavian artery (see p. 1243).
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The suprascapular vein also lies behind the clavicle, and it opens > the external jugular vein, there being a valve at or near its ending. The external jugular vein will be found described on p. 1176.
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Brachial Plexus. —The brachial plexus is situated in the lower part he posterior triangle of the neck, behind the clavicle, and in the >er part of the axilla. Its complex formation is rendered simple arranging it into four stages—namely (1) nerve-roots, (2) nervenks, (3) divisions of nerve-trunks, and (4) nerve-cords.
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First Stage .—The nerves which form the plexus are the anterior nary rami of the fifth, sixth, seventh, and eighth cervical, and the ater part of that of the first thoracic. Superiorly the plexus is lforced by a small descending branch from the fourth cervical, ich joins the fifth, and interiorly it is occasionally reinforced by a ,nch from the second thoracic, which joins the first. As regards the t thoracic nerve, the part of it which does not join the plexus, and ich is of small size, enters the first intercostal space to become the t intercostal nerve. The nerves, as thej^ emerge at the side of the k, are placed between the scalenus anterior and scalenus medius, which they give branches.
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Second Stage .—The fifth and sixth cervical nerves join at the
 +
 +
er border of the scalenus anterior to form the upper trunk ; the
 +
r enth cervical remains meanwhile single, and forms the middle nk ; and the eighth cervical and greater part of the first thoracic ite between the scalene muscles to form the lower trunk. There ! thus three trunks—upper, middle, and lower.
 +
 +
Third Stage.—A little above the clavicle each of the three trunks ^aks up into anterior and posterior divisions.
 +
 +
Fourth Stage.— The anterior divisions of the upper and middle inks unite to form the lateral cord of the plexus; the anterior dsion of the lower trunk, which is of large size, forms the medial rd; and all three posterior divisions (that of the lower trunk being small size) unite to form the posterior cord. There are thus three rds—lateral, medial, and posterior. As a variety, the anterior /ision of the middle trunk may subdivide into two branches, one tering the lateral cord and the other the medial.
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H 94
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A MANUAL OF ANATOMY
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Branches of the Plexus above the Clavicle. —The branches are c< veniently divided into two groups—supraclavicular, arising above 1 clavicle, and coming from nerve-roots and nerve-trunks; and inf clavicular, arising below the clavicle, and coming from nerve-cords.
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 +
Supraclavicular Branches .—These are muscular branches fr< the four cervical nerves to the scalene muscles and longus cervicis.
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 +
One root of the phrenic nerve (inconstant) from the front of 1 fifth cervical.
 +
 +
The Nerve to the Rhomboids. —This branch arises from the ba of the fifth cervical, close to or along with the highest root of 1
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Iug. 718. —The Brachial Plexus.
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\ ellow=spinal nerves and their branches; blue=trunks; red=lateral cord
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 +
purple=medial cord; grey=posterior cord.
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neive to serratus anterior, and it takes a backward course throu the scalenus medius.
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 +
The Nerve to the Serratus Anterior (Nerve of Bell or Posteri Thoracic Nerve). —This branch arises by three roots from the ba of the fifth, sixth, and seventh cervical nerves. The upper two ro( pierce the scalenus medius muscle below the nerve to the rhomboi( either conjointly or separately, whilst the lowest root passes in fro of the scalenus medius, and joins the trunk formed by the oth( neai the first rib. The nerve then courses behind the brachial plex and the first part of the axillary artery to the axillary surface of t serratus anterior, which it supplies.
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THE HEAD AND NECK
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ii95
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he Nerve to the Subclavius. —This small branch arises from the of the upper trunk, its fibres being derived from the fifth cer. It descends in front of the third part of the subclavian artery, passing behind the clavicle, enters the subclavius muscle on leep aspect. This nerve sometimes communicates with the nic nerve.
 +
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he Suprascapular Nerve. —This is a large nerve which arises from Dack of the upper trunk, its fibres being derived from the fifth
 +
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 +
 +
Fig. 719. —Plan of Triangles of Neck.
 +
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sixth cervical. It is directed downwards, outwards, and backds beneath the trapezius and inferior belly of the omo-hyoid to upper border of the scapula, on approaching which it meets the rascapular artery. It is distributed to the supraspinatus and ispinatus muscles and shoulder-joint.
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 +
[t will be seen that all the branches of the brachial plexus belong er to the anterior or posterior divisions, even if they come off before >e divisions become separate, and that their distribution gives a clue
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1196
 +
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A MANUAL OF ANATOMY
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to the division to which they belong. The nerves to the scale] medius and posterior, as well as that to the rhomboids, the sup scapular, and to serratus anterior, are, from their distribution, clea dorsal or posterior in their origin; while the nerves to the scale] anterior, longus cervicis, and subclavius are equally clearly anteric
 +
 +
Below the clavicle the lateral and medial cords give off all the antei branches, while the posterior come entirely from the posterior cord.
 +
 +
For the infraclavicular branches of the brachial plexus, see p. 4
 +
 +
Anterior Triangle. —This triangle is situated in front of the ster: mastoid muscle, and its base is directed upwards.
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 +
Boundaries — Anterior. —The middle line of the neck—that is say, a line extending from the chin to the upper border of the mai brium sterni. Posterior. —The anterior border of the sterno-mast muscle. Superior. —The lower border of the mandible and a 1 drawn from the angle of that bone to the mastoid process. 1 triangle is covered by the skin, superficial cervical fascia, platysr and deep cervical fascia. Superficial to the deep fascia there the following structures: the anterior jugular vein, the ramificati< of the anterior cutaneous nerve of neck, and the cervical branch of 1 facial nerve.
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 +
The anterior triangle is subdivided into three triangles by i superior belly of the omo-hyoid muscle inferiorly, and posterior be of the digastric muscle superiorly. The subdivisions from bel upwards are called muscular, carotid, and submandibular.
 +
 +
The muscular triangle is bounded anteriorly by the middle line the neck; posteriorly by the anterior border of the sterno-mastoid; a superiorly by the superior belly of the omo-hyoid.
 +
 +
The carotid triangle is bounded inferiorly by the superior be of the omo-hyoid; superiorly by the posterior belly of the digast and stylo-hyoid; and posteriorly by the anterior border of the sten mastoid.
 +
 +
The submandibular triangle (submaxillary triangle) is bound
 +
 +
postero-inferiorly by the lower part of the posterior belly of the digasti the stylo-hyoid, and by the body of the hyoid bone: antero-inferio by the mid-line of the neck; and superiorly by one half of the be of the mandible, and a line drawn from the angle of that bone to t sterno-mastoid muscle.
 +
 +
Contents of the Triangles—Muscular Triangle (Fig. 719).—The ai of this triangle is occupied by the sterno-hyoid and sterno-thyn muscles; hence the name muscular triangle. Under cover of th< muscles there are the carotid sheath with its contents, the late lobe of the thyroid gland, the trachea, and the larynx. The oesophag lies behind the trachea, with a slight inclination towards the 1 side at the root of the neck, and the recurrent laryngeal nerve 1 in the groove between the trachea and the oesophagus. The infer thyroid artery has a tortuous course inwards behind the lower p; of the carotid sheath, and the trunk of the sympathetic descer behind both.
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THE HEAD AND NECK
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1197
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arotid Triangle. —This triangle contains the upper part of the non carotid, and the beginnings of the external and internal
 +
 +
id arteries, all of which are overlapped by the anterior border
 +
le sterno-mastoid, when the connective tissue which ensheathes muscle is undisturbed. The common carotid and internal carotid ies, together with the vagus nerve, are contained within the tid sheath, and the descendens hypoglossi lies in front of the th, or within it, being situated in either case in front of the common tid artery. The sterno-mastoid artery and the superior thyroid cross the sheath near the bifurcation of the common carotid
 +
 +
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.Transverse Facial Artery
 +
 +
 +
Parotid Duct -Buccinator Muscle Facial Artery -Submental Artery
 +
 +
 +
Lingual Artery — Sup. Lar. Art. and Nerve Thyro-hyoid Muscle _. Superior Thyroid Artery
 +
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 +
 +
Inf. Belly of Omo-hyoid-,
 +
 +
Subclavian Artery (third part)
 +
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, Superficial Temporal Artery
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HPI"' Maxillary Artery
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Posterior Auriculav
 +
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r Artery
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/r _ Occipital Artery
 +
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>itW
 +
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,,,, . .-. - JIlifL. _Stylo-hyoid Muscle
 +
 +
WyMSm---- Post - Bel, y of Di s astric
 +
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!£- _Hypoglossal Nerve
 +
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-Descendens Hypoglossi
 +
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Jj_External Carotid Artery
 +
 +
 +
-Sterno-mastoid
 +
 +
Trapezius
 +
 +
_Transverse Cervical Artery
 +
 +
_. Suprascapular f\ Artery
 +
 +
 +
^iwii iin^wiu !ii wu M1 1 \w ' An '
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Fig. 720.—The Left Side of the Head and Neck. The platysma myoides has been removed.
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ry, and the carotid body lies behind the vessel about the same
 +
d. The deep cervical lymph glands lie just lateral to the course he internal jugular vein. The origins of the superior thyroid, lingual, ial, and occipital arteries are contained in this triangle, and the ending pharyngeal branch of the external carotid lies deeply between t vessel and the internal carotid. The internal jugular vein in this ingle receives the common facial, lingual, and superior thyroid veins, e hypoglossal nerve lies along the lower border of the posterioi ly of the digastric muscle, and it here gives off, fiom behind wards, the descendens hypoglossi and the nerves to thyio-hyoid
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A MANUAL OF ANATOMY
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1198
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and genio-hyoid, the former passing downwards in front of, or witl the carotid sheath, and the latter passing forwards and downwards an acute angle with the parent trunk. The internal branch of superior laryngeal nerve lies deeply behind the bloodvessels, and external laryngeal branch of that nerve descends parallel and deep the superior thyroid artery, and passes deep to the upper end of posterior border of the sterno-thyroid muscle. The vagus nerve within the carotid sheath, and the sympathetic trunk is behind The accessory nerve lies deeply, its course being downwards and ba wards beneath the sterno-mastoid, the deep portion of which usual! pierces about an inch below the angle of the mandible.
 +
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Digastric Triangle.—This triangle is divided into two parts, antei and posterior, by the stylo-mandibular ligament. The anterior p contains the superficial part of the submandibular gland, the antei facial vein being superficial to it, and the facial artery being embed( in its upper and back part. In this triangle the facial artery gives its ascending palatine, tonsillar, glandular, and submental brand The muscles in the floor of the anterior part of the triangle are mylo-hyoid and a part of the hyo-glossus. The superficial part of submandibular gland is superficial to the mylo-hyoid muscle, a conceals the mylo-hyoid nerve and submental artery, which are direct contact with the muscle. The hypoglossal nerve lies upon t] part of the hyo-glossus muscle which appears in the anterior part the triangle, but it soon disappears beneath the posterior free bon of the mylo-hyoid muscle. It is important to notice that it lies para to and just above the greater horn of the hyoid bone, which forms important structure in the floor of the triangle, and shows a little the insertion of the thyro-hyoid muscle below it.
 +
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The anterior jugular vein and the anterior cutaneous nerve of 1 neck have been already described (see pp. /1173 and 1187). 1 cervical branch of the facial nerve will be found described on p. 12
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Submandibular Lymph Glands (Submaxillary Lymphatic Glands) These glands lie upon the superficial surface of the submandibu salivary gland, under cover of the deep cervical fascia. They forn chain beneath the corresponding half of the base of the mandit which extends from near the angle of the bone to near the origin of 1 anterior belly of the digastric muscle. The central gland of the chi is closely related to the facial artery as that vessel is about to asce
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over the base of the mandible, from the following sources:
 +
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1. The front of the scalp.
 +
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2. The side of the nose.
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3. A few from the lower eyelid.
 +
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4. The lower part of the cheek.
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5. Half of the upper lip.
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6. The lateral part of the lower lip
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7. The anterior third of the lat eral border of the tongue.
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They receive their afferent vess
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8.
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9 10.
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11.
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12.
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The subjacent portion of floor of the mouth.
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Half of the upper gum.
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The lateral part of the lo^ gum.
 +
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The facial lymph glands.
 +
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The submandibular and si lingual salivary glands.
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THE HEAD AND NECK
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1199
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Their efferent vessels pass to the upper deep cervical lymph glands, ch are on a level with the upper border of the thyroid cartilage of larynx.
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The submental lymph glands lie beneath the chin, and are two or
 +
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e in number. They receive their afferent lymphatics from the tip
 +
he tongue, the front of the floor of the mouth, and the inner part the lower lip; and their efferent lymphatics pass to the subidibular lymphatic glands. It must be borne in mind that these Lphatic vessels, like those elsewhere in the body, frequently comnicate across the middle line.
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The prelaryngeal lymph glands, when present, are situated in front the crico-thyroid ligament, and are one or two in number. They give their afferent lymphatics from the interior of the larynx, dw the rima glottidis, and from the adjacent part of the thyroid nd. Their efferent lymphatics pass to the inferior deep cervical lph glands. The upper part of the larynx drains into the superior p cervical lymph glands along a course accompanying that of the >erior laryngeal vessels.
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The para- and pretracheal lymph glands lie in front and at the sides the trachea, from which, as well as from the adjacent part of the a*oid gland, they receive their afferent lymphatics. Their efferent iphatics pass to the inferior deep cervical lymph glands. Occasionally a few lymph glands are met with along the course the anterior jugular vein.
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Deep Cervical Lymph Glands. —These glands lie deep to the sternostoid muscle, and are very numerous. They are arranged in two tups, superior and inferior.
 +
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The superior deep cervical lymph glands lie along the internal
 +
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ular vein above the level of the upper border of the thyroid cartilage,
 +
ey receive their afferent lymphatics from the cranial cavity, the ernal maxillary glands, some of the parotid and submandibular nph glands, the root of the tongue, the upper part of the thyroid nd, the upper part of the larynx, and the lower part of the pharynx, eir efferent lymphatics pass to the inferior deep cervical lymph nds. One large gland of this group is very constant, and lies close the angle of the mandible. It drains the dorsum and sides of the igue, but not the tip as a rule.
 +
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The inferior deep cervical lymph glands lie along the lower part of j internal jugular vein, and extend outwards and backwards deep to
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1 sterno-mastoid as far as its posterior border. These lymph glands J continuous inferiorly with the deep cervical lymph glands lying the subclavian triangle, and, through these, with the axillary glands, ey receive their afferent lymphatics from the superior deep cervical nph glands, the upper superficial cervical lymph glands, the lower rt of the thyroid gland and larynx, and the cervical portions of the ichea and oesophagus. Their efferent lymphatics unite to form a ^gle vessel, called the jugular trunk, which opens on the left side into
 +
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2 thoracic duct, and on the right side into the right lymphatic duct.
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1200
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A MANUAL OF ANATOMY
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Infrahyoid Muscles. —These are the omo-hyoid, sterno-hyoi sterno-thyroid, and thyro-hyoid.
 +
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Omo-hyoid. —This muscle consists of two bellies, superior (anteric and inferior (posterior), and an intermediate tendon. Origin .—I means of the inferior belly from (i) the upper border of the scapu close to the inner side of the suprascapular notch, and (2) the supr scapular ligament, which bridges over the suprascapular notch.
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Insertion .—By means of the superior belly into the outer third the lower border of the body of the hyoid bone immediately later to the insertion of the sterno-hyoid muscle.
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Nerve-supply .—The superior belly is supplied by the ramus desce dens hypoglossi, and the posterior belly derives its branches from t] ansa hypoglossi.
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Greater Horn
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Lesser Horn
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Omo-hyoid (Sup. Belly)
 +
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1
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Fig. 721.—The Hyoid Bone, showing its Muscular Attachments.
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The inferior belly is contained in the posterior triangle of the nec and separates the occipital from the subclavian triangle. Its course forwards and slightly upwards, and it passes deep to the stern mastoid muscle, where its fibres terminate in the intermediate tendo It is ensheathed by a deep process of the deep cervical fascia as th fascia crosses the posterior triangle, and this process is attached to t back of the inner end of the clavicle and the first rib, which explai the almost horizontal position occupied by the inferior belly.
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The superior belly proceeds from the intermediate tendon, ai passes upwards and slightly inwards to the body of the hyoid bor As it emerges from beneath the anterior border of the sterno-mastc muscle the superior belly crosses the carotid sheath on a level wi the narrow anterior part of the cricoid cartilage, and in the anteri triangle of the neck it forms the separation between the muscular ai carotid triangles.
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THE HEAD AND NECK
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1201
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rno-hyoid — Origin. —(i) The posterior surface of the manubrium at its upper and outer part; (2) the posterior sterno-clavicular jnt; and, sometimes, (3) the posterior surface of the clavicle at Ler end.
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sertion. —The inner two-thirds of the lower border of the body of roid bone, extending from the middle line to the insertion of the or belly of the omo-hyoid. irve-supply. —The ansa hypoglossi.
 +
 +
ie muscle is flat and ribbon-like, and rests upon the sternod and thyro-hyoid.
 +
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irno-thyroid — Origin. —(r) The posterior surface of the manusterni at its upper and outer part below the origin of the sterno; and (2) the posterior surface of the first costal cartilage. sertion. —The oblique line on the -outer surface of the lamina of Lyroid cartilage.
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irve-supply. —The ansa hypoglossi. The nerves enter this and st muscle quite at the lower part of the neck, ie muscle is broader, but shorter, than the sterno-hyoid underwhich it lies. Within the thorax the right muscle lies in front 3 innominate artery, and the left in front of the left common d artery and left innominate vein. In the neck each muscle upon the carotid sheath and the corresponding right or left lobe 5 thyroid gland.
 +
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ie sterno-hyoid muscles as they leave the thorax are separated 1 interval, in which situation the sterno-thyroid muscles lie in contact. As the muscles ascend the sterno-hyoids converge, but erno-thyroids diverge.
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tyro-hyoid — Origin. —The oblique line on the outer surface of tmina of the thyroid cartilage.
 +
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\sertion. —(1) The outer half of the lower border of the body of yoid bone; and (2) the basal half of the greater horn of that
 +
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erve-supply. —A special branch of the hypoglossal, though originlerived from the first and second cervical nerves. The nerve 3 the surface of the muscle close to its posterior border, ie muscle is quadrilateral. Its superficial surface supports the ior belly of the omo-hyoid and the sterno-hyoid muscles, and its surface is related to the lamina of the thyroid cartilage, the -hyoid membrane, the internal branch of the superior laryngeal
 +
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, and the superior laryngeal artery.
 +
e nerves which supply the infrahyoid group of muscles are derived from 'st, second, and third cervicals through the hypoglossal and ansa hypo ction of the Infrahyoid Muscles — Omo-hyoid. —(1) lo depress yoid bone; and (2) to render tense the deep cervical fascia in the part of the neck.
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erno-hyoid. —To depress the hyoid bone, erno-thyroid. —To depress the thyroid cartilage.
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76
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1202
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A MANUAL OF ANATOMY
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Thyro-hyoid.— (i) To depress the hyoid bone; and (2) to ele the thyroid cartilage, as in the production of high notes, or in glutition.
 +
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Structures in the Median Line of the Neck. —The median line of neck is divisible into two regions, suprahyoid and infrahyoid.
 +
 +
Suprahyoid Region. —The innermost fibres of the two platy muscles decussate at the median line for a short distance below chin. On either side of the median line, under cover of the platy< is the anterior belly of the digastric muscle. The anterior bellic
 +
 +
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Posterior Belly of Digastric— and Stylo-hyoid Hyo-glossus Muscle and Hypoglossal Nerve
 +
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Ster. Head of St.-mas. -Crico-thyroid Muscle -
 +
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Cricoid Cartilage Lat. Lobe of Thyroid Gland
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Trapezius
 +
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Clavicular Head of Stemo-mastoid Brachial Plexus
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Subclavian Artery (third part)
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Clavicle
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Anterior 'Belly of Diga: jf Mylo-hyoid
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Body of Hyoid Bone _ Superior Belly of Omo ' - Stemo-hyoid
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Thyro-hyoid
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Thyroid Cartilage Sterno-thyroid Superior Belly of Omo Crico-thyroid Ligamen
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Stemo-hyoid
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Isthmus of Thyr Gland
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■s Inferior Thyroid y of Veins
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Cla. Head of St.-i
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,T\T
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-\r Sterno-thyroid
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Sternal Head of Sternomastoid
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Sterno-thyroid
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Sterno-hyoid
 +
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Fig. 722.—Dissection of the Front of the Neck.
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The area bounded on either side by the anterior belly of the digastric a below by the body of the hyoid bone is the submental triangle.
 +
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 +
opposite sides are near each other at the chin, but as they des< with an inclination outwards they diverge from each other, and 1 between them a triangular interval sometimes called the subm< triangle. The base of this triangle is formed by the body of the h bone, and each lateral boundary is constructed by the anterior 1 of the digastric, the apex being placed at the chin. The area oi triangle is occupied by the anterior portions of the mylo-hyoid mus which meet at the median line in a tendinous raphe, and super! to these muscles there are the submental lymph glands.
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THE HEAD AND NECK
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1203
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Epiglottis
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Greater Horn of Hyoid Bone~
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Lesser Horn of Hyoid Bone Body of Hyoid Bone-"
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Thyro-hyoid Membrane -Levator (Mandril® ) Thyroid® Muscle / Thyroid Cartilage - Crico-thyroid Ligament. Pyramidal LobeCricoid Cartilage'
 +
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Right Lobe of Thyroid Gland Isthmus
 +
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Trachea
 +
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lubmental Lymph Glands. —These glands, usually two in number,
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1 the submental triangle beneath the chin and above the body of hyoid bone, one being on either side of the median line. Each d receives its afferent vessels from (1) the medial portions of the
 +
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r lip and lower gum; (2) the tip of the tongue and adjacent portion
 +
le floor of the mouth; (3) the skin of the chin; and (4) sometimes upper lip. Their efferent vessels pass to (1) the submandibular ph glands, and (2) the ilo-omo-hyoid lymph gland, of the superior deep cer 1 lymph glands, infrahyoid Region. —The re from the hyoid bone downis to the suprasternal notch the upper border of the Lubrium sterni is of conrable importance in conion with bronchocele or re, laryngotomy, and traDtomy.
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The body of the hyoid bone
 +
 +
r well-marked structure, lg with the greater horn on er side of it. Below the id bone there is the thyroid membrane, which passes /ards within the lower borof the hyoid bone. The t structure is the thyroid kilage, the upper border of ch has a well - marked iian notch, whilst its two form by their union the minent laryngeal prominence mum Adami).
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Succeeding the thyroid carti 2 there is a narrow interval, which is occupied by the crico-thyroid iment, and immediately below this is the narrow anterior part of
 +
 +
cricoid cartilage. The crico-thyroid ligament is only exposed close the median line, being elsewhere covered by the two crico-thyroid scles. The exposed part of the ligament is crossed by the cricovoid arterial arch, which is situated midway between the thyroid 1 cricoid cartilages, and lying upon the ligament there may be i or two prelaryngeal lymphatic glands. Laryngotomy may be formed in the crico-thyroid region, and the crico-thyroid arterial h has to be borne in mind.
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 +
Succeeding the cricoid cartilage is the trachea, which, as it cends, inclines backwards, and therefore becomes somewhat
 +
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Right Bronchus^ Eparterial Bronchus, Hyparterial Bronchus.^'
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Si'- ; .
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err::.?*,
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iCZZZv
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.
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^ ".."..-A
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Left Bronchus
 +
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Fig. 723. —The Hyoid Bone, Larynx Trachea, Bronchi, and Thyroid Gland (Anterior View).
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1204
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A MANUAL OF ANATOMY
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inaccessible; at the suprasternal notch it may be i£ inches fr the surface. The thyroid gland is intimately related to it superioi Each lobe closely embraces it laterally as low as about the fifth ri and the isthmus lies in front of the second and third rings as a n but its position is liable to variation. Crossing the upper border of isthmus there is one of the branches of the superior thyroid arte known as the artery of the isthmus.
 +
 +
There is nothing of any importance in front of the trachea ab< the isthmus of the thyroid gland. Below the isthmus there is a m or less copious plexus of veins, called the inferior thyroid plexus, fr which the right and left inferior thyroid veins descend. OccasI ally a small artery, called the arteria thyroidea ima, ascends direc in front of this part of the trachea in the median line to reach i
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\c
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% \
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\ \ \ » / / / / / —V-A-A-/ / /
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phrenic ru-^ scalenus anterior'--., thyro-cervical trunk—-.
 +
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sub'elcw^ ay— scalenus medius—
 +
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vertebral vn.-vertebral ay.-
 +
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-vagus n. 'omo-hyoid
 +
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—brachial plexus
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-I 5 - 1 rib
 +
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sympathetic trunk
 +
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Z n _d r jb
 +
 +
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zura—"
 +
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oesophagus
 +
 +
long, cap. and long cer. disc, between 1st and 2nd thoracic vtb.
 +
 +
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\2 n - d thoracic tr pr '"'I s - thoracic spinous pr
 +
 +
 +
Fig. 724.—Section through Lower Part of Neck.
 +
 +
 +
isthmus of the thyroid gland. The innominate, and even the rig common carotid, artery and the left innominate vein sometirr encroach upon the front of the trachea towards the root of the nec The latter is a particularly important arrangement to remember, a: occurs more frequently in women and children. In early life t upper part of the thymus covers the front of the trachea. The foi going structures are covered by the sterno-thyroid and sterno-hyc muscles in the following manner: the two sterno-thyroid muscles a in contact with each other for a short distance above the manubriri sterni, so as to cover the trachea, but the two sterno-hyoid muse! are here separated by an interval; superiorly the two sterno-thyre muscles diverge, and the two sterno-hyoid muscles come very near together.
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THE HEAD AND NECK
 +
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1205
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he operation performed upon the trachea is tracheotomy, rding as it is performed above or below the isthmus of the thyroid 1 , it is spoken of as the high or the low operation. In the high ition there is no anatomical obstacle, unless it be a close attach: of the isthmus of the thyroid gland to the tracheal rings which vers. In the low operation the following obstacles are present: he trachea is here less accessible, because it recedes from the ,ce; (2) the inferior thyroid plexus of veins might prove trouble
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.Ansa
 +
 +
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- Ant. Jug. V. Vagus
 +
 +
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N. toThyro-hyoid
 +
 +
Int. Laryngeal Nerve
 +
 +
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Ext. Laryngeal Nerve
 +
 +
Descendens Hypoglossi Desc. Cerv.
 +
 +
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sser Occip. N. •
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Upper Cord of rachial Plexus
 +
 +
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cessory Nerve..
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Phrenic
 +
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725.— Deep Nerves in the Neck in Relation with Carotid Sheath.
 +
 +
 +
e; (3) an arteria thyroidea ima may be present; (4) the innominate right common carotid arteries and the left innominate vein may endangered; and (5) in young children the thymus would be in the
 +
 +
Fhe Ramus Descendens Hypoglossi (Descendens Cervicis Nerve).
 +
 +
ramus descendens arises from the hypoglossal nerve as the latter ks round the occipital artery, its fibres being derived from the municating branches which the hypoglossal receives from the loop
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1206
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A MANUAL OF ANATOMY
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between the first and second cervical nerves. The nerve, whicl long, passes downwards and slightly forwards, lying upon, or witl the carotid sheath, and in either case directly over the line of common carotid artery. Before reaching the centre of the necl furnishes a branch to the superior belly of the omo-hyoid mus Lower down it is joined by a branch which is formed by the unior the two rami communicantes cervicales from the anterior primary r; of the second and third cervical nerves. These two rami, howe^ sometimes join it separately. In this manner a loop is formed usu; about the level of the cricoid cartilage, which is called the ansa hy
 +
 +
 +
H.G.
 +
 +
 +
 +
Fig. 726.— Scheme of the Hypoglossal Nerve, showing its Connections with Cervical Spinal Nerves.
 +
 +
Sy., twig from sympathetic; Pn., communicating with vagus; ic, 2c, 3c, fi second, and third cervical; C.H., communicans hypoglossi; C.C., c< municantes cervicalis; D.C., descendens hypoglossi; A.B.O.H., to ante belly of omo-hyoid; A.C., ansa hypoglossi; S.H., to sterno-hyoid; S.T. sterno-thyroid; P.B.O.H., to inferior belly of omo-hyoid; T.H., to th] hyoid; G.H., to genio-hyoid; G.H.G., to genio-glossus; H.G., to hyo-gloss S.G., to stylo-glossus.
 +
 +
glossi. The convexity of the loop is directed downwards, and fr it branches are given off to (1) the sterno-hyoid, (2) the sterno-thyrc and (3) the inferior belly of the omo-hyoid muscles.
 +
 +
The fibres of the ramus descendens hyo-glossi are of spinal, not hypoglos; origin.
 +
 +
For the rami communicantes cervicales, see Cervical Plexus (p. ii£
 +
 +
The Nerve to Thyro-hyoid. —This nerve, which is composed of spf fibres derived from the loop between the first and second cervi nerves, arises from the hypoglossal at the lower border of the poster belly of the digastric. It passes forwards and downwards, formi
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THE HEAD AND NECK
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1207
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ute angle with the parent trunk, and enters the thyro-hyoid
 +
le on its superficial surface.
 +
 +
irotid Sheath. —The carotid sheath, already described on p. 1179, ived from the posterior lamina of the sheath of the sterno-mastoid le, and is intimately connected anteriorly with the pretracheal , and posteriorly with the prevertebral layer, of the deep cervical i The interior of the sheath is divided into three compartments— •, inner, and posterior. The outer and inner compartments are •ated from each other by a septum, the inner compartment containhe common carotid artery and, it may be, the ramus descendens glossi, and the outer compartment the internal jugular vein. The rior compartment is situated within the back part of the septum, contains the vagus nerve. The ramus descendens hypoglossi may pon the sheath, or within it, and the trunk of the sympathetic mds behind, and in intimate relation with it.
 +
 +
tie foregoing is the usual account of this sheath, but there are some anaits who believe that not only it, but many other fascial planes are hardly
 +
 +
 +
 +
Fig. 727.—Scheme of Section through Carotid Sheath showing
 +
 +
Contents and Certain Relations.
 +
 +
 +
mizable in the living or in the undisturbed dead body In any case, there > reason to believe that the carotid has more or less of a sheath than any r artery of its own size elsewhere.
 +
 +
[Jommon Carotid Arteries— The right common carotid artery arises 1 the innominate artery behind the upper border of the right sternoicular joint, and the left common carotid aitery arises from the er surface of the arch of the aorta, in close proximity to the origin he innominate artery. The vessel of the right side is therefore rely cervical, whilst that of the left side is partly thoracic and part y
 +
 +
The thoracic part of the left common carotid artery has alieady n described in connection with the thorax (see p. 1039)In the neck the common carotid artery of each side extends from back of the corresponding sterno-clavicular joint to the level o upper border of the thyroid cartilage of the larynx, which corrends to the disc between the bodies of the third and fourth cervica tebrse. At this level the vessel divides into the external and interna
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1208
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 +
A MANUAL OF ANATOMY
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Fig. 728. —The Aorta in
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1. Arch of the Aorta
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2. Aortic Isthmus
 +
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3. Aortic Spindle
 +
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4. Descending Aorta
 +
 +
5. Coronary Arteries (from
 +
 +
Ascending Aorta)
 +
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6. Innominate Artery
 +
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7. Left Common Carotid
 +
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8. Left Subclavian
 +
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9. Right Common Carotid
 +
 +
 +
the Thorax, and the Head and Neck.
 +
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10. Right Subclavian
 +
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11. External Carotid
 +
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12. Internal Carotid
 +
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13. Maxillary
 +
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14. Superficial Temporal
 +
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15. Vertebral
 +
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16. Internal Mammary
 +
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17. Thyro-cervical Trunk
 +
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18. Inferior Thyroid
 +
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19. Transverse Cervical
 +
 +
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Principal Arteries of i
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20. Suprascapular
 +
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21. Superior Thyroid
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22. Lingual
 +
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23. Facial
 +
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24. Occipital
 +
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25. Posterior Auricular
 +
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26. Ascending Pharyngea
 +
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27. Transverse Facial
 +
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28. Posterior Intercostals
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29. Ligamentum Arteriosum
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THE HEAD AND NECK
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1209
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rotid arteries. The place of bifurcation is sometimes opposite the dy of the hyoid bone, and, more rarely, on a level with the cricoid rtilage of the larynx. The vessel is about 3J inches long, and its urse is upwards and outwards in the direction of a line drawn from 3 sterno-clavicular joint to a point midway between the angle of 3 mandible and the mastoid process of the temporal bone. This e, as high as the level of the upper border of the thyroid cartilage, Dresents the course of the common carotid artery. At the root of e neck the two common carotid arteries are not very far apart, and e trachea lies in the intervening space. As the two vessels ascend ey become more divergent, on account of the projection of the right d left lobes of the thyroid gland and the thyroid cartilage.
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The artery, along with the internal jugular vein and vagus nerve, d, perhaps, the ramus descendens hypoglossi, is contained within e carotid sheath, already described. Opposite the cricoid cartilage is crossed by the superior belly of the omo-hyoid muscle. Below is level it lies deeply in the region of the muscular triangle, being Lder cover of the sterno-hyoid and sterno-thyroid muscles, in addition the platysma and the anterior border of the sterno-mastoid. Above is level it is situated in the carotid triangle, where it is more super:ially placed, its only muscular coverings being the platysma and the iterior border of the sterno-mastoid.
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Relations — Anterior .—The skin; superficial fascia and platysma; vesting layer of the deep cervical fascia; anterior border of the erno-mastoid; sterno-hyoid; sterno-thyroid; superior belly of the no-hyoid; and the anterior wall of the carotid sheath. Three veins oss the artery from without inwards: (1) the anterior jugular vein osses it immediately above the clavicle, superficial to the sternoA>id and sterno-thyroid muscles; (2) the middle thyroid vein just jlow the level of the cricoid cartilage; and (3) the superior thyroid jin near its bifurcation. The sterno-mastoid branch of the superior lyroid artery, which is of small size, passes obliquely downwards id outwards in front of the carotid sheath in the carotid triangle, tie ramus descendens hypoglossi descends in front of the carotid Leath to form the ansa hypoglossi.
 +
 +
Posterior .—The posterior wall of the carotid sheath; the cervical ansverse processes as high as the level of the fourth; the longus irvicis, scalenus anterior, and part of the longus capitis muscles; ie sympathetic trunk, which is intimately related to the posterior all of the carotid sheath; the recurrent laryngeal nerve; and the iferior thyroid artery, both of which latter structures pass inwards id upwards behind the lower part of the sheath.
 +
 +
Lateral .—The internal jugular vein and the vagus nerve, the latter ing between the artery and the vein, on a plane posterior to both, t the lower part of the neck, on the right side, the internal jugular ein leaves the common carotid artery, making a slight interval in hich the right vagus nerve appears as it is about to pass in front F the first part of the right subclavian artery. On the left side,
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12 IO
 +
 +
 +
A MANUAL OF ANATOMY
 +
 +
 +
however, the internal jugular vein is very closely related to the commo carotid artery, and even overlaps it.
 +
 +
Medial .—From below upwards (i) the trachea and oesophagu: with the recurrent laryngeal nerve and the inferior thyroid arter lying in the intervening groove; (2) the corresponding lobe of th thyroid gland, upon which the vessel impresses a groove, and by whic it is usually overlapped; and (3) the larynx and pharynx.
 +
 +
 +
Accessory Part of Parotid Gland
 +
 +
Parotid Gland ! _ ., ,
 +
 +
Parotid Gland
 +
 +
 +
Transverse Facial Artery i
 +
 +
 +
Superficial Temporal Artery Maxillary Artery
 +
 +
 +
Mental Branch of Inferior Dental | Artery
 +
 +
 +
Facial Artery Lingual Artery
 +
 +
 +
Inferior Thyroid Artery_
 +
 +
 +
 +
__ Posterior Auricula Artery
 +
 +
 +
\Occipital Artery
 +
 +
 +
Greater Occipital Nerve
 +
 +
Internal Carotid Artery
 +
 +
 +
External Carotid Artery.I Superior Laryngeal Artery , Superior Thyroid Artery
 +
 +
Vagus Nerve ( Internal Jugular Vein l C ommon Carotid Artery V
 +
 +
Superior Belly of Omo-hyoid __ Ascending Cervical Artery _.J
 +
 +
 +
Deep Cervical " Lymph Glands
 +
 +
 +
Phrenic Nerve
 +
 +
 +
! \
 +
 +
Subclavian Artery (first part) \
 +
 +
 +
 +
Scalenus Anterior Muscle
 +
 +
Transverse Cervict Artery
 +
 +
 +
\ Suprascapular Artery Thyro-cervical Trunk
 +
 +
 +
Fig. 729.—Deep Dissection of the Left Side of the Neck
 +
 +
(after Spalteholz).
 +
 +
 +
The common carotid artery, as a rule, gives off no branch. Th superior thyroid artery, however, may arise from it superiorly, and i some cases the ascending pharyngeal artery.
 +
 +
Surgery—Compression. —The part of the vessel most favourabl situated for compression lies in front of the tubercle of the transvers process of the sixth cervical vertebra, this tubercle, known as th carotid tubercle, being on a level with the cricoid cartilage of the larynx Ligation. —The part of the vessel most favourably placed fo ligation is situated on a level with the cricoid cartilage just abov the point where it is crossed by the anterior belly of the omo-hyoi'
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THE HEAD AND NECK
 +
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1211
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,cle. The structures to be avoided in the operation are: (i) the us descendens hypoglossi upon, or it may be within, the sheath; the internal jugular vein and vagus nerve, both of which are lin the sheath, and upon the outer side of the artery; and (3) the ipathetic trunk, which lies behind and in close contact with the ith. The small sterno-mastoid branch of the superior thyroid
 +
 +
ry will probably be cut, as it passes obliquely downwards and
 +
wards over the sheath in the carotid triangle. Ligation of the
 +
 +
ry below the level of the cricoid cartilage is attended with diffi
 +
y, the vessel being here covered by the sterno-hyoid and sternoroid muscles, in addition to the platysma and sterno-mastoid.
 +
the left side the internal jugular vein is an additional difficulty. Collateral Circulation after Ligation. —(1) Cross anastomoses take
 +
 +
e freely between the external and internal carotid arteries of
 +
losite sides. (2) The inferior thyroid artery of the side operated ►n anastomoses freely with the superior thyroid of the same side, ch is a branch of the external carotid. (3) The deep cervical nch of the superior intercostal, which latter is a branch of the Dnd part of the subclavian artery on the right side, and of the t part on the left side, anastomoses with the descending branch the occipital, which is a branch of the external carotid. (4) The tebral artery undergoes much enlargement.
 +
 +
Carotid Body.— This small body is situated behind the common otid artery close to its bifurcation. It is composed of a few lobules ted by connective tissue, and it receives minute twigs from the acent part of the common carotid artery. The lobules consist groups of polyhedral cells permeated by blood-capillaries and apathetic nerve-filaments. Some of the cellular constituents are omaffin cells, similar to those which are met with in the medulla the suprarenal gland and in the sympathetic ganglia. These cells derived from the contiguous ganglia of the sympathetic system, e carotid body of each side is similar to the glomus coccygeum 1 organs of Zuckerkandl.
 +
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The carotid body is developed in part from the sympathetic system, and in
 +
 +
t from the lymphatic system. # _ , ,, , ,
 +
 +
Development.— The common carotid arteries are developed from the parts of ventral aortae which are situated between the third and fourth aortic arches.
 +
 +
Internal Jugular Vein. —The internal jugular vein is the continuon of the intracranial sigmoid sinus. It begins in the posteroeral compartment of the jugular foramen, and ends behind the ler end of the clavicle by joining the subclavian to form the j nn o~ nate vein. At its beginning it has a slight dilatation, called the berior bulb. The vein descends vertically, lying at first on the outer e of the internal carotid, and then on the outer side of the common ~otid artery, the vagus nerve being interposed in each case, and being enclosed within the carotid sheath. The relations of the ssel for the most part correspond to those of the artenes which 1
 +
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companies.
 +
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1212
 +
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A MANUAL OF ANATOMY
 +
 +
 +
Tributaries.—These are as follows:
 +
 +
 +
Pharyngeal. Superior thyroid. Middle thyroid.
 +
 +
 +
Inferior petrosal sinus.
 +
 +
Common facial.
 +
 +
Lingual.
 +
 +
A small vein accompanying the occipital artery may occasional open into it.
 +
 +
Hypoglossal Nerve
 +
 +
Second Cervical Nerve / Occipital Artery
 +
 +
 +
Accessory
 +
 +
Nerve
 +
 +
 +
Lesser Occipital Nerve
 +
 +
 +
Great Auricular Nerve
 +
 +
 +
R am i Communicantes ( Cervicales \
 +
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Fourth Cervical Nerve
 +
 +
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Descending Branch of Fourth Cervical Nerve
 +
 +
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Supraclavicular Nerves
 +
 +
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External Jugular
 +
 +
vd " (ci '° /if
 +
 +
Nerve to Subclavius jdjP®®
 +
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Subclavian Vein
 +
 +
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 +
Vagus Nerve
 +
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Nerve to Thyro-hyoid Muscl
 +
 +
 +
Terminal Branches M Hypoglossal Ner
 +
 +
 +
Internal Laryngea Nerve
 +
 +
 +
External Larynge; Nerve
 +
 +
— Ramus Descenden Hypoglossi
 +
 +
-Nerve to Superior I
 +
 +
of Omo-hyoid Ansa Hypoglossi
 +
 +
 +
 +
Anterior J ugular V
 +
 +
- -. Internal Jugular V
 +
 +
 +
v //i/lfJM
 +
 +
 +
Fig. 730. —Deep Dissection of the Right Side of the Neck (after
 +
 +
Hirschfeld and Leveill£).
 +
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1, upper part of sterno-mastoid; 2, trapezius; 3, tendon of omo-hyoid.
 +
 +
 +
The inferior petrosal sinus leaves the cranial cavity through th antero-medial compartment of the jugular foramen, and opens int the internal jugular vein close to the base of the skull.
 +
 +
Development. —The internal jugular vein is developed from the anteric cardinal vein.
 +
 +
The vagus nerve in the neck will be found described on p. 1327.
 +
 +
External Carotid Artery.—The external carotid artery is one c the terminal branches of the common carotid, the other being th internal carotid artery. In spite of its name, it is, at its origin, th medial of the two vessels, and it lies anterior to, and nearer the media
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THE HEAD AND NECK
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1213
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than, the internal carotid. It extends from a point on a level 1 the upper border of the thyroid cartilage to one immediately ind the neck of the mandible, where it divides in the substance of parotid gland into the superficial temporal and maxillary arteries, s about 2J inches in length, and its direction is at first upwards forwards as far as the angle of the mandible, and then upwards backwards. At first the artery lies in the carotid triangle, and is iparatively superficial. As it leaves this triangle it is more deeply
 +
 +
ed, being crossed by the posterior belly of the digastric and styloid muscles, and the hypoglossal nerve. Then the vessel is eroded in the substance of the parotid gland, where it is crossed from
 +
ind forwards by the facial nerve.
 +
 +
Relations.— Antero--lateral. —The skin; superficial fasciaplatysma; p fascia; anterior border of the sterno-mastoid; the lingual and imon facial veins; the hypoglossal nerve (all the foregoing being grior relations, whilst the artery lies in the carotid triangle); the terior belly of the digastric and stylo-hyoid muscles; the greater t of the parotid gland; the posterior facial vein; and the facial ve. Deep or Postero-medial. —(1) The stylo-pharyngeus muscle,
 +
 +
so-pharyngeal nerve, and styloid process of the temporal bone,
 +
of which lie between the vessel and the internal carotid (the latter g lying on a plane behind the external carotid); and (2) a small tion of the parotid gland. The pharynx and hyoid bone; the erior laryngeal nerve; a portion of the parotid gland; and the terior border of the ramus of the mandible.
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 +
The external carotid artery has no vein in the sense of a companion sel, but the posterior facial vein descends superficially to it in the otid gland to near the angle of the mandible, beyond which point artery has no vein.
 +
 +
The course of the vessel may be indicated by a line drawn from side of the cricoid cartilage of the larynx to the tragus of the icle.
 +
 +
Development. —The external carotid artery is, for a short portion of its rse, the persistent part of the ventral aorta above the level of the third aortic 1. In the rest of its extent it is formed from enlarged side-branches of the inal stem.
 +
 +
Branches.—These are arranged in four sets ending, and terminal—and are as follows:
 +
 +
Anterior. Posterior. Ascending.
 +
 +
'erior thyroid. Occipital. Ascending
 +
 +
glial. Posterior auricular. pharyngeal.
 +
 +
ial.
 +
 +
Superior Thyroid Artery.—This vessel arises in the carotid tiiangle m the front part of the external carotid close to its oiigin. It
 +
 +
es an arched course forwards and downwards, passing undei covei
 +
the infrahyoid muscles. On reaching the apex of the corresponding >e of the thyroid gland it breaks up into its terminal branches,
 +
 +
 +
—anterior, posterior,
 +
 +
Terminal.
 +
 +
Superficial temporal. Maxillary.
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 +
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1214
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A MANUAL OF ANATOMY
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which enter the lobe on its superficial aspect, and anastomose free within it with branches of the inferior thyroid artery, and in the isthm with its fellow of the opposite side.
 +
 +
Branches:
 +
 +
Infrahyoid. Crico-thyroid
 +
 +
Sterno-mastoid. Glandular.
 +
 +
Superior laryngeal. Muscular.
 +
 +
The infrahyoid artery passes inwards on the thyro-hyoid membrar deep to the thyro-hyoid muscle, and close to the lower border of i
 +
 +
 +
Fig. 731. —Dissection of Carotid Triangle.
 +
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hyoid bone. It anastomoses at the middle line with its fellow of t opposite side, and with the suprahyoid branch of the lingual arte: of the same side. The sterno-mastoid branch passes obliquely downwar. and outwards, lying superficial to the carotid sheath, to enter the de< surface of the muscle from which it takes its name. It is liable to cut in tying the common carotid artery. The superior laryngeal arte accompanies the internal laryngeal nerve, and, passing deep to tj outer border of the thyro-hyoid muscle, pierces the thyro-hycl membrane, to be distributed to the interior of the larynx. The cril thyroid branch passes transversely inwards upon the crico-thyrC ligament, and anastomoses with its fellow of the opposite side to foil
 +
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 +
Hypoglossal
 +
 +
 +
Digastric Post. Belly
 +
 +
Comm. Facial V.
 +
 +
N. Desc. Hypog. Sup. Laryng. N. Inf. Constrict.
 +
 +
 +
. Laryng. N. >uter div.)
 +
 +
Sup. Thyr. V.
 +
 +
Omo-hyoid
 +
 +
Sterno-hyoid
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THE HEAD AND NECK
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1
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1215
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crico-thyroid arch. The glandular branches are distributed to the responding lobe of the thyroid gland. They anastomose freely h branches of the inferior thyroid of the same side, and with branches the fellow of the opposite side to a less extent. One very constant .nch, known as the artery of the isthmus, courses along the upper -der of the isthmus, and anastomoses with its fellow of the opposite e. The muscular branches are distributed to the infrahyoid muscles. The superior thyroid vein issues from the upper part of the corremding lobe of the thyroid gland, and crosses in front of the common otid artery near its bifurcation to open into the internal jugular n. Its tributaries for the most part correspond to the branches the artery.
 +
 +
Lingual Artery. —The lingual artery arises from the front part of i external carotid a little above the origin of the superior thyroid d opposite the greater horn of the hyoid bone. From its comcated course it is convenient to divide the artery into three parts.
 +
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 +
Dorsum of Tongue
 +
 +
Sublingual Gland (turned >
 +
 +
UP) !
 +
 +
 +
Stylo-glossus Muscle N Lingual Nerve
 +
 +
x
 +
 +
 +
 +
Submandibular Ganglion
 +
 +
Submandibular Gland (deep part)
 +
 +
^Facial Artery
 +
 +
 +
Mandible . (in section)
 +
 +
 +
Genio-glossus Muscle , (
 +
 +
Genio-hyoid Muscle ! Sublingual Artery Arteria Profunda Linguae
 +
 +
 +
_Lingual Artery
 +
 +
_Sup. Thy. Artery
 +
 +
. Ext. Car. Artery
 +
 +
\ \ Vena Comitans Hypoglossi
 +
 +
t Hypoglossal Nerve
 +
 +
Submandibular Duct
 +
 +
 +
Fig. 732.—Deep Dissection of the Left Submandibular Region.
 +
 +
 +
First Part. —The first part of the vessel ascends for a little, and en, bending sharply, descends to the greater horn of the hyoid bone, issing deep to the posterior belly of the digastric and stylo-hyoid uscles. So far the vessel lies in the carotid triangle, and the bend tiich it describes is crossed by the hypoglossal nerve. It is for the ost part comparatively superficial.
 +
 +
Second Part. —The second part passes horizontally forwards along ie upper border of the hyoid bone deep to the hyo-glossus, the hypoossal nerve and its vena comitans being superficial to that muscle, eep to it is the middle constrictor. At the anterior border of the ^o-glossus it enters upon the third part of its course.
 +
 +
Third Part.— Near the anterior border of the hyo-glossus muscle ie lingual artery describes another sharp bend in an upward direction, id ascends almost vertically to the under surface of the tongue,
 +
 +
sting upon the genio-glossus, and being under cover of the anterior
 +
irder of the hyo-glossus. Having reached the tongue, the artery
 +
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 +
 +
 +
 +
 +
1216
 +
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 +
A MANUAL OF ANATOMY
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 +
 +
passes forwards on its under surface in a tortuous manner under th name of arteria profunda linguae.
 +
 +
Branches:
 +
 +
1. Suprahyoid. 3. Sublingual.
 +
 +
2. Rami dorsales linguae. 4. Arteria profunda linguae.
 +
 +
The suprahyoid artery arises from the lingual at the posterior horde of the hyo-glossus, and passes along the upper border of the hyof bone.
 +
 +
The rami dorsalis linguce arise under cover of the hyo-glossn muscle, which they pierce, and so reach the posterior third of th
 +
 +
 +
Superficial Temporal \
 +
 +
Occipital
 +
 +
Maxillary
 +
 +
Posterior Auricular
 +
 +
 +
Transverse Facial
 +
 +
 +
Supraorbital
 +
 +
Supratrochlear
 +
 +
 +
 +
Angular
 +
 +
Lateral Nasal
 +
 +
Superior Labial Inferior Labial
 +
 +
 +
Submental Submandibular Gland
 +
 +
 +
Internal Carotid '
 +
 +
 +
External Carotid
 +
 +
 +
Lingual
 +
 +
Suoerior Thyroid
 +
 +
 +
Fig. 733. —The Arteries of the Right Side of the Head (after
 +
 +
L. Testut’s ‘ Anatomie Humaine ’)•
 +
 +
dorsum of the tongue. They are distributed to the mucous membran and substance of the tongue, the tonsil, and the soft palate.
 +
 +
The sublingual artery arises close to the anterior border of th hyo-glossus muscle. It supplies the sublingual gland, the adjacen muscles, and the mucous membrane of the floor of the mouth. On of the lateral branches anastomoses at the median line with a com sponding branch of the opposite artery, and another of them is know as the artery of the frenulum linguce.
 +
 +
The arteria profunda linguce [ranine artery) is the terminal pai of the lingual. It passes forwards on the under surface of the tongu< lying immediately lateral to the insertion of the genio-glossus, betwee
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 +
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 +
THE HEAD AND NECK
 +
 +
 +
1217
 +
 +
id the longitudinalis linguae inferior. It is more or less embedded le substance of the tongue, and its course is tortuous in adaptation tie mobility of the organ to which it is so intimately related. ToIs the tip of the tongue the vessel is very superficially placed, close by the side of the frenulum linguae, and it anastomoses l its fellow of the opposite side near the tip. Elsewhere the cross domoses are remarkable for their absence, and if one lingual artery led with fine injection hardly any crosses the mid-line of the tongue pt at the tip. The arteria profunda linguae furnishes branches y to the substance of the tongue. Its close relation to the frenulum rae is to be carefully noted in connection with the operation for f of tongue-tied children.
 +
 +
rhe lingual veins are as follows: (1) the vena comitans hypoglossi ine vein), which is of large size, commences under the tip of the pe, and passes backwards, in company with the hypoglossal nerve,
 +
 +
rficial to the hyo-glossus muscle, receiving tributaries from the
 +
ounding structures; (2) two vence comitantes accompanying the ral artery; and (3) the dorsal lingual veins, which originate in a us beneath the mucous membrane over the posterior third of the .n. These three sets of veins may join into a common trunk, called lingual vein, which opens into the internal jugular vein, or they r terminate independently in that vein.
 +
 +
jingual Lymph Glands.—These glands, which are of small size, pon the outer surfaces of the genio-glossus and hyo-glossus muscles, g the vena comitans hypoglossi. They are really small glandions lying in the course of the lymphatic vessels of the tongue hese pass to join the deep cervical lymph glands.
 +
 +
Facial Artery.—The facial artery arises from the front part of external carotid in the carotid triangle immediately above the nal artery, or sometimes in common with that vessel. It passes ards and forwards deep to the hypoglossal nerve, the posterior 7 of the digastric and the stylo-hyoid muscles, into the submanilar triangle. It then becomes embedded in a groove on the upper back part of the submandibular gland, its general course being ^ards with many curves. From this groove it describes a sharp i upwards over the base of the mandible in front of the masseter cle. The vessel then enters upon the facial part of its course, for scription of which see p. 1278.
 +
 +
Branches. —Four branches arise from the cervical part of the facial ry:
 +
 +
1. Ascending palatine. 3. Glandular.
 +
 +
2. Tonsillar. 4. Submental.
 +
 +
rhe ascending palatine artery passes upwards between the stylosus and stylo-pharyngeus muscles, and then over the upper ler of the superior constrictor of the pharynx along with the levator ti muscle. It is distributed to the soft palate, tonsil, and auditory The tonsillar artery passes upwards between the stylo-glossus
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77
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1218
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A MANUAL OF ANATOMY
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and medial pterygoid muscles, and, after piercing the superior c< strictor muscle, it is distributed to the tonsil and the posterior p of the side of the tongue. The glandular branches axe distributed the submandibular gland. The submental artery arises from i facial just below the mandible, and passes forwards superficial the mylo-hyoid muscle. It gives branches to the submandibular gla and mylo-hyoid muscle, some of the branches piercing that mus to reach the sublingual gland and anastomose with the subling artery.
 +
 +
The cervical part of the anterior facial vein passes downwai and backwards superficial to the submandibular gland. Hav: received tributaries corresponding to the branches of the cervical p of the artery, it unites with the anterior division of the posterior fac vein to form the common facial vein, which opens into the inter: jugular opposite the body of the hyoid bone.
 +
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Occipital Artery. —The occipital artery arises from the poster aspect of the external carotid opposite the facial artery. It pas
 +
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at first upwards and sligh
 +
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UATERfll
 +
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J>IC,
 +
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r rvi T. CAROT.
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MX 1.
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NJ.X 11
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occ i P.
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ARTERV.
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Fig. 734.—Plan of Course of Occipital Artery in Neck.
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backwards beneath the poster belly of the digastric and sty hyoid muscles, and the hy] glossal nerve, having hool round it, passes forwards sup ficial to it. Having reached level of the interval between 1 transverse process of the at and the mastoid process, ' artery changes its course, a passes backwards to occupy occipital groove on the in: aspect of the mastoid proc( where it is in touch with rectus capitis lateralis. In t backward course it crosses
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internal carotid artery, internal jugular vein, and vagus, accessc and hypoglossal nerves. As it lies in the occipital groove the ve< is very deeply placed, being covered by the following structui (1) the origin of the posterior belly of the digastric; (2) the lon$ simus capitis; (3) the splenius capitis; and (4) the sterno-mastc After escaping from beneath the splenius capitis, the vessel takes upward course superficial to the semispinalis capitis to the occip: region, where it ramifies in a tortuous manner along with the branc of the greater occipital nerve.
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Branches. — Muscular; meningeal; mastoid; descending; s Occipital.
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The muscular branches are distributed to the adjacent muse one of them, the sterno-mastoid branch, crosses the hypoglossal ne: and enters the deep surface of the sterno-mastoid muscle in comps
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THE HEAD AND NECK
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1219
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the accessory nerve. The meningeal branch accompanies the internal lar vein, and enters the cranial cavity through the jugular foramen apply the dura mater of the posterior fossa. The mastoid branch es through the mastoid foramen when present, and supplies the cent dura mater. The descending and the occipital [terminal) Lches have been already described (see p. 1146).
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 +
Tie description of the occipital veins will be found on p. 1147. tosterior Auricular Artery. —This vessel arises from the posterior ct of the external carotid a little above the origin of the occipital ry, and above the posterior belly of the digastric. It passes ards and slightly backwards under cover of the lower part of the tid gland, and behind the styloid process of the temporal bone, g crossed by the facial nerve. Having reached the groove between back of the auricle and the mastoid process, where it meets the erior auricular nerve, it divides into two branches, auricular and aital.
 +
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branches. —These are as follows: muscular; glandular; stylotoid; auricular; and occipital.
 +
 +
rhe muscular branches supply the adjacent muscles. The glandular ches are distributed to the lower part of the parotid gland. The -mastoid artery enters the facial canal through the stylo-mastoid men. It is distributed to the tympanic cavity and the mastoid
 +
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ells, and anastomoses with the tympanic branch of the first part
 +
ae maxillary artery. With this latter branch it forms a ring at the lmference of the tympanic membrane on its inner aspect. Within facial canal the stylo-mastoid artery anastomoses with the super1 petrosal branch of the middle meningeal artery, which branch rs the canal through the hiatus for greater superficial petrosal r e. The auricular branch passes upwards deep to the auricularis erior muscle, and furnishes branches to the inner aspect of the
 +
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le, some of which reach the outer surface by piercing the cartilage
 +
by turning round its margin. The auricular branch anastomoses l the posterior branch of the superficial temporal artery. The 'ntal branch passes backwards over the mastoid process to the pital region, and anastomoses with the occipital artery, rhe posterior auricular vein, of fairly large size, often unites with posterior division of the posterior facial vein near the angle of inferior maxilla, and by this union the external jugular vein is led. The arrangement, however, is very variable.
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Ascending Pharyngeal Artery. —This long, slender vessel arises from beginning of the deep surface of the external carotid. It runs ically upwards towards the base of the skull, lying very deeply 1 the longus capitis muscle, and between the internal carotid ry, in front of which it has passed, and the pharynx, branches :
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1. Pharyngeal. 3. Prevertebral.
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2. Palatine. 4. Inferior tympanic.
 +
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5. Meningeal.
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1220
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A MANUAL OF ANATOMY
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The pharyngeal branches are distributed to the pharynx. TJ palatine branch passes over the superior constrictor muscle of t] pharynx, and is distributed to the soft palate, auditory tube, and tons The prevertebral branches supply the prevertebral muscles. T] inferior tympanic artery passes with the tympanic branch of the gloss pharyngeal nerve through the tympanic canaliculus in the petro part of the temporal bone, and so reaches the tympanic cavity, to t] inner wall of which it is distributed. The meningeal branches are t' terminal branches of the ascending pharyngeal, and are three in numbe One passes through the foramen lacerum, a second through the jugul foramen, and a third through the anterior condylar canal, to be d: tributed to the dura mater in the vicinity of these foramina.
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The descending pharyngeal vein accompanies the ascending phary
 +
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geal artery.
 +
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For the superficial temporal and maxillary branches of the extern carotid artery, see pp. 1158 and 1304.
 +
 +
The internal carotid artery will be found described on p. 1323.
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Thyroid Gland. —The thyroid gland is situated on either side the upper part of the trachea and larynx, and a small portion of it li in front of the upper part of the trachea. Its size is subject to mu variation; its weight is rather more than 1 ounce; and it is larger the female than in the male. It consists of right and left lobes and; isthmus.
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Each lobe is conical and about 2 inches long, the rounded ba being directed downwards. It extends from the middle of the lami: of the thyroid cartilage to about the level of the fifth ring of the trache Its superficial surface , which looks forwards and outwards, is somewb convex, and is covered by the sterno-thyroid, sterno-hyoid, and superi belly of the omo-hyoid muscles. It is also overlapped by the anted border of the sterno-mastoid. Its deep surface is concave in adaptati to the trachea and larynx. The anterior border is thin, and towar its lower part is connected with that of the opposite lateral lobe means of the isthmus. The posterior border is thick, and is in conta with the pharynx and oesophagus, and has the parathyroid glan embedded in it. Each lobe overlaps the corresponding common carol artery, enclosed in the carotid sheath, and is frequently grooved by tb vessel. Interiorly it overlaps the recurrent laryngeal nerve and infer] thyroid artery. The apex of each lobe rests upon the inferior constrict muscle of the pharynx, and the superior thyroid artery enters it sup< ficially and deeply4
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The isthmus is inconstant as regards size and position. Its dep ranges from J to 1 inch, and its breadth is about \ inch. It conne^ the lower parts of the anterior borders of the lateral lobes, but dc not reach quite so low as their bases. .It lies in front of the trach< usually upon the second and third rings, and fits closely to the rir upon which it rests. Along its upper border there is a branch of t superior thyroid artery, known as the artery of the isthmus, which an. tomoses with its fellow of the opposite side. From its lower bore
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THE HEAD AND NECK
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1221
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?ral veins issue, which take part in the inferior thyroid plexus of is in front of the trachea.
 +
 +
In some cases an additional lobe is present, called the pyramidal !. It forms a long pyramid, which is attached by its base to the ier border of the isthmus, usually at its junction with the left lobe, apex is attached to the body of the hyoid bone by a fibrous band, ch sometimes contains muscular fibres, known as the levator glandulcz oidce muscle. It is seldom quite median in position.
 +
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erior Belly of Digastricand Stylo-hyoid lyo-glossus Muscle and’ Hypoglossal Nerve
 +
 +
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Head of Sterno-mastoid Crico-thyroid Muscle Cricoid Cartilage t Lobe of Thyroid Body
 +
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Trapezius vicular Head of
 +
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7 / 7 ,
 +
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sterno-mastoid Brachial Plexus
 +
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Subclavian Artery (third part)
 +
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Clavicle
 +
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Anterior Belly of Digastric L Mylo-hyoid
 +
 +
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Body of Hyoid Bone
 +
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Superior Belly of Omo-hyoid Sterno-hyoid
 +
 +
K ljnimr- Thyro-hyoid
 +
 +
USSr - Laryngeal Prominence "m sterno-thyroid
 +
 +
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Superior Belly of Omo-hyoid Crico-thyroid Membrane
 +
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Sterno-hyoid
 +
 +
 +
Isthmus of Thyroid Gland
 +
 +
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Inferior Thyroid Plexus of Veins — - Cla. Head'd St.-mas. Sterno-thyroid
 +
 +
Sternal Head of Sternomastoid
 +
 +
 +
Fig. 735
 +
 +
he area bounded below by the
 +
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Sterno-thyroid
 +
 +
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Sterno-hyoid
 +
 +
—Dissection of the Front of the Neck.
 +
 +
on either side by the anterior belly of the digastric and body of the hyoid bone is the submental triangle.
 +
 +
 +
The thyroid gland is invested by a fibrous sheath which is derived u the pretracheal layer of the deep cervical fascia.
 +
 +
When a portion or portions of the pyramidal lobe, or of the right or lobes, become detached, the isolated masses are known as accessory roids.
 +
 +
Blood-supply—Arteries. —The thyroid gland is very vascular. The • sries on either side are (i) the superior thyroid, which is a branch of external carotid; and (2) the inferior thyroid, which is a branch of thyro-cervical trunk of the first part of the subclavian. Occasion7 there is a third thyroid artery, called the arteria thyroidea ima, ich is derived from the innominate artery, or from the arch of the
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1222
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A MANUAL OF ANATOMY
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aorta, and is distributed to the isthmus, its position being in fro of the trachea at the median line, or close to it.
 +
 +
The veins are superior, middle, and inferior. The superior ai middle thyroid veins open into the internal jugular. The inferi thyroid veins, right and left, issue from a plexus of veins in front the trachea below the isthmus. The left vein opens into the 1 < innominate vein, whilst the right may open into the left innomina vein, into the angle of junction of the right and left innominate veil or into the lower part of the right innominate vein.
 +
 +
Nerves. —These are derived from the sympathetic plexuses whi accompany the superior and inferior thyroid arteries.
 +
 +
Lymphatics. —The lymphatic vessels the thyroid body are disposed in t groups —ascending and descending. T ascending lymphatics form three sets median and two lateral, right and le The median ascending lymphatics retn lymph from the upper part of the isthmi and pass to the prelaryngeal lym glands. The lateral ascending lymphat on either side accompany the super thyroid artery, and pass to the infer deep cervical lymph glands on a level wi the cricoid cartilage of the larynx. T descending lymphatics also form three st The median descending lymphatics retr lymph from the lower part of the isthm and pass to the pretracheal lymph glam The lateral descending lymphatics on eitl side accompany the inferior thyroid artery, and pass to the pa: tracheal lymph glands, which lie in the groove between the tract and oesophagus, the efferents of which terminate in the inferior de cervical lymph glands.
 +
 +
Structure. —The thyroid gland has an external capsule of dense connect tissue which sends trabeculae into the interior, thereby dividing it into irregu lobules. These lobules are composed of groups of closed vesicles, which ; connected together by areolar tissue. The vesicles are oval or spherical, a each is lined with a single layer of columnar or cubical epithelium. They cont; a yellowish viscid, albuminous fluid called colloid and are surrounded by n works of capillary bloodvessels.
 +
 +
Development. —The thyroid body is developed from the entoderm of 1 ventral wall of the pharyngeal portion of the primitive gut.
 +
 +
The first indication of the median thyroid is an evagination of the vent pharyngeal entoderm immediately behind the tuberculnm impar. This evagu tion is called the median thyroid diverticulum. It forms a thick-walled epithe. vesicle embedded in mesoderm, which soon becomes solid. As the vesicle grc its distal end becomes bilobed. Superiorly it retains for a little time its co munication with the ventral wall of the pharynx behind the tuberculum im] by a hollow pedicle, which constitutes the thyro-glossal duct (canal of H This duct usually disappears, its superior orifice being represented on the dorsi of the adult, tongue by the blind recess, called the foramen ccecum. In very r;
 +
 +
 +
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Fig. 736. — Section of the Thyroid Gland, showing the Vesicles and their Epithelial Lining.
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The colloid is indicated.
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THE HEAD AND NECK
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1223
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the lingual portion of the duct may persist for a short distance, in which the foramen caecum leads to the lumen of a short tube, known as the ductus %lis.
 +
 +
tie median thyroid, as stated, gives rise to the isthmus and lobes of the thyroid gland.
 +
 +
tie median bud almost from its beginning is in contact with the pericardial and the two ventral aortae arising from the truncus arteriosus; it extends these vessels. It lies in loose mesoderm ventral to the condensations e second and third visceral arches. As the head grows forward and the irdium assumes in consequence a more caudal position, the thyroid bud h has separated from its lingual attachment) remains in contact with the irdium and the vessels; thus it moves caudally with reference to the pharynloor above it, and as a result of its lateral extension at the same time along vessels, comes into relation with the ventral angle of the fourth lateral 1 (P- 77 )■ Becoming attached to this, its farther caudal dislocation is
 +
 +
>ed, save perhaps in the middle line, where some of its cells may still follow Dericardium in its retrogression. The main part of the bud, however, ins in its fixed position, and forms the lobes and isthmus, he ventral bud from the fourth pouch is sometimes termed the lateral id bud, being supposed to contribute to the formation of each lobe. It is •ally believed, however, that it does not do so, but remains as a small elial mass in the lobe; under some circumstances it appears to show a
 +
 +
ncy to thyroid vacuolization.
 +
□nnective tissue derived from this mesodermic investment now invades the mass, and it is broken up into numerous solid epithelial cords, which
 +
 +
omose freely, and so give rise to an intricate reticulum, the meshes of which
 +
ccupied by connective tissue and bloodvessels of mesodermic origin. The epithelial cords of the reticulum become hollow, and the lumina so produced )roken up at intervals by constrictions into closed vesicles , which contain olloid material.
 +
 +
he pyramidal lobe of the thyroid gland sometimes met with in connection the isthmus of the adult thyroid is developed from the median bud. he epithelial cells of the vesicles of the adult thyroid are derived from the lerm of the pharyngeal part of the fore-gut.
 +
 +
Parathyroid Glands. —The parathyroids are four in number, and are tiged in pairs. The upper pair are related to the dorsal borders ie lobes of the thyroid gland, and the lower pair are placed behind ower ends of the lobes. They are difficult to distinguish with the id eye, but the best way to find them is to follow the anastomosis reen the superior and inferior thyroid arteries. They are developed ^aginations of the entoderm of the third and fourth visceral pouches ther side. The parathyroids present no traces of closed vesicles he colloid material.
 +
 +
ccessory Thyroid Glands. —These glands are sometimes met in the neighhood of the hyoid bone, and are known as the suprahyoid and prehyoid !S. They are developed as buds or evaginations of the thyroglossal duct, they consist of thyroid tissue.
 +
 +
 +
The Trachea and (Esophagus.
 +
 +
trachea. —The trachea extends from the cricoid cartilage of the nx to about the level of the disc between the bodies of the fourth fifth thoracic vertebrae, where it divides into the two bronchi, t and left. Its average length is about inches, and its width
 +
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1224
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A MANUAL OF ANATOMY
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about i inch. Anteriorly and laterally it is cylindrical and fi but posteriorly it is flattened and membranous, so that it does press upon the oesophagus, in front of which it lies. It occupie medial position, and its direction is downwards with an inclinat backwards. It is divisible into two parts, cervical and thoracic.
 +
 +
For the trachea in the thorax, see p. 1085.
 +
 +
The cervical part of the trachea extends from the cricoid cartil to the level of the upper border of the manubrium sterni, and it measr about 2 \ inches in length. It is freely movable, and is surroun<
 +
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by areolar tissue, which c
 +
 +
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Epiglottis
 +
 +
 +
Greater Horn of Hyoid Bone Lesser Horn of Hyoid Bone_
 +
 +
Body of Hyoid Bone —
 +
 +
 +
Thyro-hyoid Membrane —
 +
 +
Levator Glandulae \ Thyroidm Muscle/
 +
 +
Thyroid Cartilage - Crico-thyroid Ligament Pyramidal Lobe f Cricoid Cartilage Right Lobe of Thyroid Gland _
 +
 +
Isthmus
 +
 +
Right Bronchus Eparterial Bronchus
 +
 +
 +
Hyparterial Bronchus.._ f
 +
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 +
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Trachea
 +
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 +
tains many elastic fibres, ; is somewhat loosely arrange Relations — A nterior. —' isthmus of the thyroid gli lies directly upon the sect and third rings as a rule, first ring usually lying expo between its upper border 1 the cricoid cartilage. Su] ficial to the first ring, on left of the median line, th may be the lower part of pyramidal lobe of the thyi gland. Below the isthmus the inferior thyroid plexus veins, from which the ri and left inferior thyroid v( pass downwards one on eit side of the median line. ' arteria thyroidea ima may cend to the isthmus of thyroid gland, lying in fr of the trachea at the med line, or slightly to the right it. The anterior jugular ve:
 +
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Fig.
 +
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Left Bronchus
 +
 +
737 .-The Hyoid Bone, Larynx, r ig ht and J eft - are a " teri “ Trachea, Bronchi, and Thyroid Gland it, and just above the ma (Anterior View). brium sterni it is crossed by
 +
 +
communicating branch wh passes between these two veins. In children under two years age the cervical portion of the thymus forms an important ante] relation. Close to the upper border of the manubrium sterni innominate artery may encroach slightly upon it. The pretract layer of the deep cervical fascia forms an anterior relation, as \ as the superficial layer of that fascia, which is here usually descril as dividing to form the suprasternal space above the supraster notch. Another, and perhaps more common-sense, description is say that in front of the trachea is a layer of cellular tissue c
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THE HEAD AND NECK
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1225
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Lateral Thyrohyoid Ligament
 +
 +
Upper Border of Thyroid Cartilage
 +
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Epiglottis
 +
 +
 +
— Cartilago Triticea
 +
 +
_Corniculate Cartilage
 +
 +
-Arytenoid Cartilage
 +
 +
f_i.__Cricoid Cartilage
 +
 +
ft 3
 +
 +
Vfj--Right Lobe of Thyroid Body
 +
 +
 +
)us with that in which the thyroid gland is embedded, and that tissue increases in thickness from before backward as the lea recedes from the surface on approaching the thorax. Other rior relations are the anterior jugular veins, along with one or two )h glands, and in some cases the left innominate vein. The sternod and sterno-thyroid muscles cover it in the following manner: derno-hyoid muscles are separated by an interval below, but they 3 nearly into contact above; and the sterno-thyroid muscles are intact below, but diverge above. Between the muscles of opposite 1 there is a very narinterval, along which trachea is free from cular covering. lateral .—The trachea fiosely embraced on sr side by the lobes he thyroid gland as as about the level of fifth ring, and lateral this is the carotid .th with its contents, common carotid artery g nearest the lobe.
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 +
Posterior .—The trachea n front of the cesogus, which projects a e to its left side tods the root of the neck, ween the two there is groove, in which the irrent laryngeal nerve inferior laryngeal
 +
 +
ry ascend. For a reflce to the high and
 +
operations of tracheny, see p. 1174.
 +
 +
Blood-supply. —The ar- , ,,
 +
 +
es of the cervical part of the trachea are derived from the m or thyroid of each side, which is a branch of the thyro-cervica nk
 +
 +
The veins terminate in the inferior thyroid plexus and inferioi
 +
 +
roid veins. . , , ,
 +
 +
The lymphatics pass to the inferior deep cervical lymph glands
 +
 +
Pretracheal Lymph Glands. —These glands lie upon the front of e deal part of the trachea, below the isthmus of the thyroid gland, fir afferent vessels are derived from the front of the trachea, an lower part of the isthmus of the thyroid gland. Their efferent sels pass to the inferior deep cervical lymph glands. The lymphatic
 +
 +
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Fig. 7^8.—The Epiglottis, Larynx, Trachea, Bronchi, and Thyroid Gland (Posterior View).
 +
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1226
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A MANUAL OF ANATOMY
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vessels of the cervical part of the trachea pass to the pretrache; inferior thyroid, and inferior deep cervical lymph glands.
 +
 +
Nerve-supply.— The nerves are derived from the vagus, recurre: laryngeal, and sympathetic.
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 +
 +
Structure. —The trachea is composed of about twenty so-called rings hyaline cartilage, which are incomplete posteriorly. They serve to keep t tube permanently open for the transmission of air, and are embedded in fibro tissue, which also connects together their contiguous borders. They are hon shoe shaped, and each forms rather more than two-thirds of a circle, being fl externally and convex internally. The deficient portions of the rings are plac posteriorly, and here each ring ends in two round extremities. The inters between these extremities are bridged over by fibrous tissue continuous wi that which connects the borders of the rings and in which they are embedde
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In some cases a ring m;
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Ciliated Epithelium Basement Membrane
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Mucosa
 +
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_ Elastic Fibres
 +
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Submucosa, with Mucous Glands
 +
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Hyaline Cartilage of Ring
 +
 +
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Fibrous Investment
 +
 +
 +
Fig. 739. —Longitudinal Section of the
 +
 +
Trachea.
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 +
end in a bifurcated e tremity, or it may jc one of the adjacent rin^ The lowest ring is dee and its lower border pr jects backwards so as form a ridge betwe the openings of the t\ bronchi.
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 +
In the posterior w< of the trachea within t fibrous layer there is continuous layer of u: striped muscular tissu the fibres of which e tend transversely betwe* the ends of the rings which they are attache In the intervals betwe< the extremities of ti rings they are attach* to the fibrous coat. The fibres serve to approj mate the ends of t] rings, and so diminish t] calibre of the tube.
 +
 +
 +
The submucous coat consists of loosely-arranged areolar tissue, and contai] the larger bloodvessels and nerves, together with the mucous glands.
 +
 +
The mucous coat consists of areolar and elastic tissues, and a large amoui of lymphoid or adenoid tissue. It contains the ramifications of the arteri and nerves, as well as the lymphatics. Superficial to the mucosa there is well-marked basement membrane which supports the epithelium. The dee portion of the mucosa consists principally of elastic fibres. On the poster! wall these elastic fibres are very numerous, and are arranged in longitudin bundles which give rise to elevations of the mucosa.
 +
 +
The epithelium is of the stratified columnar ciliated variety.
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The wall of the trachea contains many mucous glands. Some of these a situated in the submucous coat. Others, which are of large size, lie on t posterior wall, where they are very superficial, many of them appearing li small grains superficial to the fibrous layer. Others are contained within t. fibrous layer. The ducts of these glands have to pass through the muscula elastic, and mucous walls of the tube.
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Development. —The trachea is developed from the lower part of the laryng
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THE HEAD AND NECK
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1227
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ial tube from the ventral aspect of the fore-gut superiorly, the upper part is diverticulum giving rise to the larynx.
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Esophagus.—The oesophagus is that part of the alimentary canal h extends from the pharynx to the stomach. In the neck it ns on a level with the lower border of the cricoid cartilage, and on a level with the upper border of the manubrium sterni. It >mpressed from before backwards and between the trachea and the vertebral mn covered by the longus cervicis cles. At first it occupies the median but as it descends it inclines slightly ie left side, so as to be partly visible on left side of the trachea, delations— Anterior. —The trachea; the
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erior parts of the lobes of the thyroid
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y ; the recurrent laryngeal nerves; and inferior thyroid arteries. Posterior. —The ebral column and the longus cervicis icles covered by the prevertebral cellular ie. Lateral. —On either side there is the )tid sheath with its contents. The right left recurrent laryngeal nerves are inately related to the oesophagus, and md on each side in the groove between nd the trachea.
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The cervical part of the oesophagus reres its blood-supply from the inferior roid arteries, which accompany the corDonding recurrent laryngeal nerves.
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Paratracheal Lymph Glands (Inferior rroid Lymph Glands).—These glands lie the groove between the cervical parts of trachea and oesophagus, along the course the inferior thyroid artery and recurrent ^ngeal nerve. Their afferent vessels are ived from (1) the lower part of the lobe p IG —schematic View
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the thyroid body, and (2) the adja- of CEsophagus.
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it parts of the trachea and oesophagus.
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eir efferent vessels pass to the inferior deep cervical lymph glands. For a description of the oesophagus in the thoiax, including its
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ucture and development, see p. 1087. .
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Suprahyoid Region—Muscles—Digastric. The digastric muscle isists of two bellies, posterior and anterior. Origin. The posterior ly arises from the mastoid notch on the inner aspect of the mastoid ft of the temporal bone; and the anterior belly arises from the distric fossa on the inner surface of the base of the mandible close to
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"symphysis.
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Insertion. —The two bellies end upon an intermediate tendon,
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1228
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A MANUAL OF ANATOMY
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about 2 inches long, which is inserted by means of a broad fibr band into the anterior surface of the body of the hyoid bone at outer part, and the adjacent portion of the greater horn.
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Nerve-supply .—The posterior belly is supplied by the facial nei and the anterior belly by the mylo-hyoid branch of the inferior den a branch of the mandibular nerve.
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The posterior belly is directed downwards and forwards, and anterior belly downwards and slightly outwards.
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Action .—To elevate the hyoid bone, as in the act of deglutiti and to depress the mandible.
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Relations. —The posterior belly is at first deeply placed, be overhung by the mastoid process, and lying under cover of the Ion simus capitis, splenius capitis, and sterno-mastoid muscles. It is ; overlapped by the lower part of the parotid gland. It crosses external and internal carotid arteries, internal jugular vein, ;
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hypoglossal nerve, stylo-hyoid muscle above it, and the hy glossal nerve below it a short distance. i intermediate tendon embraced by the fibres the stylo-hyoid mus This tendon crosses hypoglossal nerve, ; forms two sides of a angle, known as the angle of Lesser, the b of which is directed wards, and is formed the hypoglossal nerve. In the area of this triangle is a portion the hyo-glossus muscle, and deep to this is the lingual artery. 1 anterior belly, which is shorter than the posterior, is covered the integument, platysma, and deep cervical fascia. It rests u{ the mylo-hyoid muscle, and forms part of the floor of the digasl triangle. Its inner border is connected with that of its fellow b] fascial expansion.
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The posterior belly of the digastric, along with the stylo-hyoid muscle, the stapedius muscle, is associated with the posterior end of the second vise or hyoid arch. The nerve of this arch is the facial nerve, and this explains nerve-supply of the posterior belly.
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The anterior belly is associated with the anterior or medial end of the ) visceral or mandibular arch. The nerve of this arch is the mandibular from trigeminal nerve, thus accounting for the nerve-supply of the anterior belly Stylo-hyoid — Origin .—The posterior and outer aspect of the sty! process of the temporal bone near its base.
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Insertion .—The anterior surface of the hyoid bone at the junct of the body and greater horn.
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5TVIOHVOIP
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Fig. 741. —Plan of Main Deep Relations of Digastric in Anterior Triangle.
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THE HEAD AND NECK
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1229
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erv e-supply. —The facial nerve.
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he muscle is directed downwards and forwards.
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ction. _To draw the hyoid bone upwards and backwards.
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he muscle lies close above the posterior belly of the digastric, before taking insertion, it usually splits into two bundles, which ■ace the intermediate tendon of the digastric. It is morphological delamination of the same sheet as the posterior belly of the di•ic, which explains its nerve-supply.
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[ylo-hyoid — Origin. — The mylo-hyoid line of the mandible. nsertion— The posterior fibres are inserted into the anterior surface .e body of the hyoid bone; and the principal part of the muscle is ted into a central fibrous raphe, which extends from the symphysis ti on its deep and lower aspect to the body of the hyoid bone.
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Mandible
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Raph
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)-hyoid Muscle - Lingual Nerve
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Deep Part of nandibular Gland Post. Belly of Digastric Hypoglossal Nerve Stylo-hyoid
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Body of Hyoid Bone
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e
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Infrahyoid Muscles
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Fig. 74 2.—The Mylo-hyoid Region. Anterior belly of digastric removed.
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Nerve-supply. —The mylo-hyoid branch of the inferior dental nerve, ch is a branch of the mandibular nerve.
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The muscle is directed downwards and f01 wards.
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Action.— To raise the floor of the mouth, and, in doing so, to ss the tongue against the hard palate, as in the first stage of the of deglutition; to elevate the hyoid bone, and diaw it forwards,
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L to depress the mandible. .
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The two mylo-hyoid muscles form a muscular floor for the buccal
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ity, which is known as the diaphragma oris. >
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Relations —Superficial or Inferior .—The anterior belly of the ditric; the superficial part of the submandibular gland, lodging a 'tion of the facial artery; and the mylo-hyoid nerve and submenta mch of the facial artery.
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1230
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A MANUAL OF ANATOMY
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Posterior Border .—Passing deep to the posterior free border of muscle there are the following structures, in order from above do wards: (i) the lingual nerve; (2) a portion of the submandibular gla and (3) the hypoglossal nerve and its vena comitans.
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Deep or Superior. —The hyo-glossus muscle, external to which the lingual nerve, the submandibular ganglion, the deep part of the s mandibular gland and the submandibular duct, the hypoglossal ne and its vena comitans. In front of the hyo-glossus is the genio-h} muscle, and between it and the hyo-glossus is a portion of the gei glossus, with the sublingual gland resting upon it.
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Genio-hyoid— Origin. —The inferior genial tubercle of the mand close to the symphysis on its deep aspect.
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insertion .—The inner two-thirds of the anterior surface of body of the hyoid bone over its upper part. At its insertion the mu is divided externally into two laminae, anterior and posterior, former of which extends farthest out upon the hyoid bone. The ini most fibres of origin of the hyo-glossus pass inwards between tl two laminae.
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N erv e-supply. —The hypoglossal nerve, the branch of which is garded as being composed of spinal fibres.
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The muscle is directed downwards and slightly backwards.
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Action. —To elevate the hyoid bone and draw it forwards, and depress the mandible.
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The muscle is in intimate contact with its fellow of the oppo side at the median line. Its inferior or superficial surface is cove by the mylo-hyoid, and its superior or deep surface is related to lower or posterior border of the genio-glossus.
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Genio-glossus— Origin. —The upper genial tubercle of the mand close to the symphysis on its deep aspect.
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Insertion. —The under surface of the tongue close to the med line, and extending from near the tip to the root; very slightly i the inner part of the anterior surface of the body of the hyoid b close to its upper margin; and slightly into the side of the phary where the fibres blend with those of the middle constrictor muscle.
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N erv e-supply. —The hypoglossal nerve, the branches of which er the outer surface of the muscle.
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The upper or anterior fibres arch upwards and forwards, and lower downwards and backwards, whilst the intervening fibres spr out in a fan-like manner.
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Action. —The entire glossal fibres depress the tongue at the med line, and, along with those of the opposite side, they give rise to antero-posterior groove on the dorsum of the organ; the postei glossal fibres draw forwards the tongue, causing its tip to be protru< from the mouth; the anterior glossal fibres retract the tip of the ton] when it has been protruded from the mouth; and the lower or postei (hyal) fibres elevate the hyoid bone, and draw it forwards.
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The muscle is fan-shaped. The medial surface is closely app] to that of its fellow of the opposite side. The lateral surface is rela
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THE HEAD AND NECK
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1231
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ie longitudinalis inferior muscle, the arteria profundae linguae, the glossus and stylo-glossus muscles, and the sublingual gland. The rior border is covered by the buccal mucous membrane, and the r or posterior border by the genio-hyoid muscle, lyo-glossus— Origin. —The greater horn of the hyoid bone over its •e length; the anterior surface of the body of the bone over about uter half; and the lesser horn (inconstant). The innermost fibres rigin from the hyoid bone lie between the two laminae of the geniod muscle.
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Tip of Styloid Process of Temporal Done
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Fig. 743. —The Extrinsic Muscles of the Tongue. The longitudinalis inferior is an intrinsic muscle.
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Insertion —The posterior half of the under surface of the tongue se to its lateral border, the fibres being situated medial to those of ! stylo-glossus, and both sets of fibres being intimately intermixed
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h each other and with the intrinsic lingual muscles.
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Nerve-supply .—The hypoglossal nerve, the branches of which enter
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i superficial surface. , .. , .
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The muscle is for the most part directed upwards, but its anterior
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res have a slight inclination forwards.
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Action .—To depress the side of the tongue, and, along with its low, to render the dorsum of the organ convex; and to assist m
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xacting the protruded tongue.
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The hyo-glossus is a flat, four-sided muscle.
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1232
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A MANUAL OF ANATOMY
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Relations — Superficial. —The mylo-hyoid muscle; the intermedi tendon of the digastric, and stylo-hyoid muscle; the lingual nerve, w the submandibular ganglion lying a little below it; the deep part of submandibular gland, and the submandibular duct; the hypoglos nerve; and the vena comitans hypoglossi. Posterior Border .—The : lowing structures pass deep to this border in order from above do\ wards: the glosso-pharyngeal nerve; the stylo-hyoid ligament; and lingual artery. Deep .—The posterior part of the genio-glossus; a port of the middle constrictor muscle of the pharynx; the lingual arte the lower end of the stylo-hyoid ligament; and the glosso-pharyng nerve.
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The fibres of the hyo-glossus which arise from the lesser horn the hyoid bone are separated from the rest of the muscle by th< fibres of the genio-glossus which take insertion into the side of i
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Hyo-glossus Glosso-pharyngeal N.
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Lingual N.-\ _
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Hyo-glossus-_
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Submandibular Duct-A - __
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Vena Comitans Hypoglossi—\_ Al
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Hypoglossal N.---X — ^
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- -Longitudinalislnfi Stylo-glossus
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Sublingual Gland Ant. Facial V. and Fat - Deep Submandibular G 1 • Sup. Submandibular Giant ' Mylo-hyoid
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-/- Stylo-hyoid
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~ —/Digastric
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Hyoid Bone
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\ ' Stylo-hyoid Lig.
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Lingual ArteryA 'Middle Constrictor
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Fig. 744.—Coronal Section through Submandibular Region.
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pharynx, and they are vestigial remains of the chondro-glossus monkeys. These fibres, however, are inconstant.
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Stylo-glossus — Origin .—The front of the styloid process of t temporal bone near its tip; and the upper extremity of the sty. mandibular ligament.
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Insertion .—The under surface of the tongue close to its latei border. The fibres extend as far forwards as the tip, and are situat lateral to the fibres of the hyo-glossus, both sets of fibres being in mately intermixed with each other, and with longitudinalis inferi muscle.
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Nerve-supply .—The hypoglossal nerve.
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The muscle is directed downwards, forwards, and inwards.
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Action. —(1) To draw the tongue backwards; and (2) to elevate t root of the tongue.
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Stylo-hyoid Ligament. —This is a narrow fibrous cord which attached superiorly to the tip of the styloid process, and interiorly
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THE HEAD AND NECK
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1233
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lesser horn of the hyoid bone. Its direction is downwards and ards, superficial to the glosso-pharyngeal nerve and deep to the rnal carotid artery, and its lower extremity is covered by the glossus muscle. It is liable to become ossified more or less pletely.
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rhe ligament represents the usually unossified skeletal part of the nd visceral arch, and ossification in it, when it occurs, corresponds le epihyal bone of lower mammals, so well seen in the ruminants, lubmandibular Gland (Submaxillary Gland).—This gland is situated he anterior part of the digastric triangle. It consists of a large jrficial part and a small deep part. The superficial part superiorly ipies the submandibular fossa on the inner surface of the body of mandible, and inferiorly it is covered by skin, superficial fascia, platysma, and ) fascia. The anterior facial vein deds superficial to it. Its deep surface 3 anteriorly upon the mylo-hyoid muscle,
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1 the intervention of the mylo-hyoid ^e and submental branch of the facial ry; and posteriorly upon the hyo-glossus, slightly upon the posterior belly of the istric and stylo-hyoid muscles. The jrficial part is grooved at its upper and £ part by the facial artery, which lies >edded in the gland. Posteriorly the jrficial part is related to the cervical ion of the parotid gland, from which s separated by the stylo-mandibular ment. The deep part of the gland is of .11 size, and is continuous with the superficial part at the posterior ier of the mylo-hyoid muscle. It lies under cover of that muscle n the hyo-glossus, and is related to the sublingual gland.
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Ihe submandibular duct (Wharton’s duct) emerges from the deep set of the superficial part of the gland close to the posterior border he mylo-hyoid muscle. It is about 2 inches in length, and passes ards upon the hyo-glossus muscle, lying beneath the deep part of gland. In this situation it has the submandibular ganglion and ual nerve above it, and the hypoglossal nerve below it. After dng the hyo-glossus muscle, the duct lies superficial to the geniossus, and, passing slightly upwards, it is crossed from above down'ds by the lingual nerve. Having passed just below the mucous nbrane of the floor of the mouth on the inner side of the sublingual id, the duct opens upon the floor of the mouth by a minute orifice, ch is situated on the summit of a papilla lying close to the side of frenulum linguae.
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The submandibular gland corresponds to the posterior half of the ly of the mandible, and sometimes reaches down below the level of hyoid bone.
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Lumen of Alveolus
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Crescents of Gianuzzi
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Fig. 745.—Section of the Submandibular Gland of a Dog.
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78
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A MANUAL OF ANATOMY
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1234
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Blood-supply.—The gland derives its blood chiefly from the cerv part of the facial artery.
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Nerve-supply.—The nerves are derived from the submandibi ganglion, and through this from the chorda tympani, the lingual, < the sympathetic plexus on the facial artery.
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Lymphatics.—These pass to the submandibular lymph glands, < thence to the superficial and deep cervical lymph glands.
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Structure. —The submandibular gland is a muco-serous gland, and its gen structure is similar to that of the parotid gland. The essential difference tween the two has reference to the alveoli or acini, and the nature of t secretion. The cells of the parotid alveoli are serous or albuminous. The 1 mandibular alveoli contain around the lumen mucous cells filled with gran mucigen, which is discharged as mucus. They, however, also contain s< albuminous cells, known as the marginal cells, which are situated externa
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Parotid Duct
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the mucous cells, but within the membrana propria of the alveolus. Th cells usually form groups which, from their crescentic arrangement, are knc as the crescents of Gianuzzi.
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Development. —The submandibular gland is developed as a solid outgro of the buccal epithelium. This outgrowth undergoes ramifications, and fl subsequently become hollow. The outgrowth takes place from the floor of sulcus between the tongue and the mandibular arch, far back in its lateral p at the beginning of the second month. The lingual nerve passes to the ton below the floor of the sulcus in front of the outgrowth. The submandibular d is gradually produced from before backwards by the closing off of the lov part of the sulcus, so that it really corresponds with the original floor of groove. Thus it possesses a lumen from its earliest stages, while the glan< still solid, and the lingual nerve has to pass below it.
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Sublingual Gland.—This is the smallest of the salivary glands, '< resembles an almond in shape. It measures about i\ inches in len£ and is situated beneath the mucous membrane of the floor of mouth, where it gives rise to a mucous fold, called the plica sublingua
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THE HEAD AND NECK
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1235
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iriorly it rests upon the mylo-hyoid muscle, and is here related to deep part of the submandibular gland, the submandibular duct, L the lingual nerve. Laterally it occupies the sublingual fossa on inner surface of the body of the mandible above the mylo-hyoid and medially it is in contact with the genio-glossus muscle. Its dial extremity comes into contact with its fellow of the opposite 3 over the anterior border of the genio-glossus muscle.
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The sublingual ducts (ducts of Rivini) vary in number from ten to
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nty. A few of them open into the submandibular duct, but the
 +
jority open in a linear manner upon the summit of the plica sub;ualis.
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Blood-supply.—The gland receives its blood from the sublingual rich of the lingual artery.
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Nerve-supply.—The nerves are derived from the chorda tympani 1 lingual nerves, and the sympathetic plexus on the facial artery, means of a branch of the submandibular ganglion, which is con:ted to the sublingual gland by the lingual nerve.
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Structure. —-The sublingual gland is a mucous gland, and its general structure imilar to that of the parotid and submandibular glands, but the lobules are re loosely arranged. The cells of the sublingual alveoli are for the most part cous cells, but there are also serous or albuminous cells.
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Development.— The sublingual gland is developed as a number of outgrowths 21 the buccal epithelium. These undergo ramifications, and subsequently
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ome hollow.
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Scalene Muscles and Subclavian Artery.
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Scalene Muscles.—The scalene muscles 5 three.
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Scalenus Anterior (Scalenus Anticus)—
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igin .—By four short tapering tendons )m the anterior tubercles of the transrse processes of the third, fourth, fifth, d sixth cervical vertebrae.
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Insertion .—The scalene tubercle of the st rib.
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Nerve-supply .—The anterior primary mi of the fifth and sixth cervical nerves.
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The muscle is directed downwards, itwards, and forwards.
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Action .—To fix the first rib in ordinary spiration, and to elevate it in forced spiration; and to bend the neck to one le.
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Chief Relations — Anterior. —The irenic nerve, which crosses the muscle diquely downwards and inwards; the ternal jugular vein, which lies in front of its origin; the subclavian iin close to its insertion; the thoracic or the right lymphatic duct;
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Anterior.
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A MANUAL OF ANATOMY
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1236
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the transverse cervical and suprascapular arteries; and the omo-hy muscle. Posterior. —The scalenus medius, with the intervention of second part of the subclavian artery, the nerve-roots of the bract plexus, and the cupola of the pleura. Medial. —The ascending cervi artery and the origin of the longus capitis.
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Scalenus Medius — Origin. —By six short tapering tendons from posterior tubercles of the transverse processes of the lower six cervi vertebrae.
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Insertion. —The upper surface of the first rib from the groove the subclavian artery backwards to the tubercle. Sometimes a i fibres are inserted into the suprapleural membrane (Sibson’s fasc over the cupola of the pleura. When distinct they are called 1 scalenus pleuralis.
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Nerve-supply. —The anterior primary rami of cervical nerves fr the third to the eighth inclusive.
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The muscle is directed downwards and outwards.
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Action. —(1) To fix the first rib in ordinary inspiration, and (2) bend the neck to one side.
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Relations — Anterior.— The cervical plexus, the nerve-roots of 1 brachial plexus, except the first thoracic, and the second and th parts of the subclavian artery. Posterior. —The levator scapulae a scalenus posterior muscles.
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The scalenus medius is pierced by the following nerves: the nei to the rhomboids, which passes in a backward direction; and the up] and middle roots of the nerve to serratus anterior. These two roi usually emerge from the muscle as a single cord, and the lower or th root of the nerve descends in front of the scalenus medius, and jo the foregoing cord about the level of the first rib.
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Scalenus Posterior (Scalenus Posticus) — Origin. —By two or th short tendons from the posterior tubercles of the transverse proces of the lower two or three cervical vertebrae.
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Insertion. —The upper part of the outer surface of the second in front of the insertion of the highest slip of the serratus poster superior, and behind the origin of a portion of the first and the seco digitations of the serratus anterior.
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Nerve-supply. —The anterior primary rami of the sixth, seven and eighth cervical nerves, the branches of which pass through 1 scalenus medius.
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The muscle is directed downwards and outwards.
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 +
Action. —To elevate the second rib, and to extend the neck.
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The scalenus posterior is the vestige of an important extensor muscle of neck in pronograde mammals, in which it is attached to several ribs. In orthograde position, however, with its balanced head, the need for it has ( appeared.
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Relations — Anterior. —The scalenus medius. Posterior. —The lov two tendons of origin of the levator scapulae. The scalenus poster is intimately connected with the scalenus medius, of which it is pn tically a part.
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THE HEAD AND NECK
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1237
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Subclavian Artery.—The right subclavian vessel arises from the )minate artery behind the right sterno-clavicular joint on a level 1 its upper part, and the left subclavian vessel arises from the >er aspect of the arch of the aorta towards its back part. On each the artery ends at the outer border of the first rib by becoming axillary artery. In its course the vessel is crossed superficially the scalenus anterior muscle, which divides it into three parts.
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Rectus Capitis Anterior
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Rectus Capitis Lateralis -
 +
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Basilar Part of Occipital Bone
 +
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Longus Capitis
 +
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Scalenus Posterior
 +
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Vertebral Artery (third part)
 +
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Scalenus Anterior. Scalenus Medius .
 +
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Longus Cervicis(upper oblique part) _Vertebral Artery (second part)
 +
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_Longus Cervicis (vertical part)
 +
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Vertebral Artery (first part)
 +
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HP. Longus Cervicis (lower oblique part)
 +
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Scalene Tubercle
 +
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Fig. 748. — The Right Prevertebral Muscles. The vertebral artery is also shown.
 +
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The first part extends from the origin of the vessel to the inner
 +
 +
der of the scalenus anterior; the second part lies behind that muscle;
 +
I the third part extends from the outer border of the muscle to the ter border of the first rib. The. total length of the vessel on the ht side is about 3 inches, and on the left about 4 i inches. The ery describes an arch in front of the apex of the corresponding lg and pleura, and the height to which it rises above the clavicle
 +
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ibout inch.
 +
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First Part of the Right Subclavian Artery.—This part extends from i bifurcation of the innominate artery behind the light sterno
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Fig. 749.—Right Subclavian Artery in situ: Jugular and Subclavia
 +
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Veins Removed.
 +
 +
ficially. The internal jugular and vertebral veins cross it from abc downwards close to the scalenus anterior, the latter vessel being belli the former, and the anterior jugular vein crosses it from within 0 wards, but superficial to the sterno-hyoid and sterno-thyroid muse] The vagus and its cervical cardiac branches, the cervical card branches of the sympathetic, and the nerve-loop known as the ai
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1238
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A MANUAL OF ANATOMY
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clavicular joint, on a level with its upper part, to the inner border the scalenus anterior muscle. Its direction is upwards and out war and it lies very deeply.
 +
 +
Relations— Anterior .—The skin, superficial fascia and platysr deep cervical fascia, clavicular origin of the sterno-mastoid, and ster hyoid and sterno-thyroid muscles. Three veins are related to it sup
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THE HEAD AND NECK
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1239
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. 750.—The Aorta in the Thorax, and the Principal Arteries of the
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Head and Neck.
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t. Arch of the Aorta Aortic Isthmus l- Aortic Spindle p Descending Aorta 5. Coronary Arteries (from Ascending Aorta)
 +
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5 . Innominate Artery 7 • Left Common Carotid 3 . Left Subclavian ?• Right Common Carotid
 +
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10. Right Subclavian
 +
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11. External Carotid
 +
 +
12. Internal Carotid
 +
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13. Maxillary
 +
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14. Superficial Temporal
 +
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15. Vertebral
 +
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16. Internal Mammary
 +
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17. Thyro-cervical Trunk
 +
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18. Inferior Thyroid
 +
 +
19. Transverse Cervical
 +
 +
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20. Suprascapular
 +
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21. Superior Thyroid
 +
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22. Lingual
 +
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23. Facial
 +
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24. Occipital
 +
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25. Posterior Auricular
 +
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26. Ascending Pharyngeal
 +
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27. Transverse Facial
 +
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28. Posterior Iutercostals
 +
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29. Ligamentum Arteriosum
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1240
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A MANUAL OF ANATOMY
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subclavia also cross it superficially. Posterior .—The recurrent lan geal nerve, sympathetic trunk, fat, longus cervicis muscle, first thora vertebra, cupola of the pleura, and apex of the lung. Inferior .—1 recurrent laryngeal nerve, part of the ansa subclavia, and the pleura
 +
 +
The right subclavian and right internal jugular veins unite in fr< of this part of the vessel to form the right innominate vein.
 +
 +
First Part of the Left Subclavian Artery.—This part extends fr< the upper aspect of the arch of the aorta, towards its back part, the inner border of the scalenus anterior muscle. It is therefore plac at first in the thoracic cavity. Its course is almost vertical until reaches the root of the neck, where it curves sharply outwards upon 1 cupola of the pleura, and so reaches the scalenus anterior. The re tions of the intrathoracic portion have been described in connect] with the thorax (see p. 1040).
 +
 +
Cervical Relations— Anterior .—The skin, superficial fascia a platysma, deep cervical fascia, clavicular origin of the sterno-masto sterno-hyoid, and sterno-thyroid muscles, and the thoracic duct whi arches over it. The left internal jugular and subclavian veins un
 +
 +
in front of it to form the left innomim vein, and the left vertebral vein descer in front of it under cover of the left interi jugular vein. Posterior .—The sympathe trunk with the inferior cervical ganglk fat, and the left longus cervicis muse Right. —The trachea, oesophagus, left : current laryngeal nerve, and thoracic du The varieties in origin of the subclavi artery have been described in connecti with the arch of the aorta (see p. 1040 seq.).
 +
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Second Part of the Subclavian Artery.
 +
 +
This portion of the vessel is situated behi the scalenus anterior muscle. It lies abo \ inch above the clavicle, and forms t highest part of the arch described by t vessel.
 +
 +
Relations— Anterior. — Its only din anterior relation is the scalenus anteri< Posterior .—The pleura. Superior. —T nerve-roots of the brachial plexus. 1 ferior .—The pleura.
 +
 +
In some cases the second part of the vessel passes through the scalenus ariter and in rare cases it passes in front of the muscle.
 +
 +
 +
 +
Fig. 751. —Left Subclavian Vessels and Terminal Piece of Thoracic Duct.
 +
 +
 +
For the third part of the subclavian artery see p. 1191.
 +
 +
 +
Development. —The right subclavian artery as far as the origin of the inter] mammary artery is developed from the fourth right aortic arch.
 +
 +
The left subclavian artery is developed from the seventh left, segmen arterv.
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THE HEAD AND NECK
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1241
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Branches of the subclavian artery are the vertebral, internal nmary, thyro-cervical trunk, and superior intercostal. The first
 +
 +
e arise from the first part of the artery towards its termination, and
 +
last arises from the second part on the right side, and from the
 +
 +
part on the left side.
 +
Vertebral Artery. —This, the first branch on the right side, arises n the upper and back part of the artery about an inch from its ^n, and on the left side from the vessel just after it enters the root he neck. It passes for a short distance upwards, backwards, and htly outwards, and disappears from view by entering the foramen isversarium in the sixth cervical vertebra as a rule. It then ascends tically through the successive foramina transversaria above that of sixth vertebra, passing outwards between the axis and atlas, ving traversed the foramen transversarium of the atlas, it passes kwards and inwards, lying in vertebrarterial groove on the )er surface of the posterior arch the atlas behind the superior icular process, pierces the dura ter and arachnoid, and having ched the side of the spinal d, it turns upwards and forrds in the subarachnoid space,
 +
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I enters the cranial cavity ough the foramen magnum, gradually inclines from the eral to the ventral aspect of
 +
 +
medulla, and at the lower
 +
rder of the pons it joins its low to form the basilar artery.
 +
 +
On account of its complicated arse, the vertebral artery is dded into four parts—namely, first or cervical, second or costoms verse, third or suboccipital, and fourth or intercranial.
 +
 +
The first part extends from the origin of the vessel to the foramen insversarium in the transverse process of the sixth cervical vertebra, lies between the scalenus anterior and longus cervicis muscles, ving the internal jugular and vertebral veins in front of it, being assed by the inferior thyroid artery, and having the sympathetic ank and the transverse process of the seventh cervical vertebra hind it. The vessel of the left side has the thoracic duct as an .ditional anterior relation.
 +
 +
The first part gives off no branches. . . .
 +
 +
The second part traverses the foramina transversaria ol the cervical
 +
 +
rtebrae from, as a rule, the sixth upwards. It is surrounded by t e
 +
rtebral venous plexus, and by the vertebral plexus of the s}/mpaetic, and it lies in front of the cervical spinal neives as these emerge
 +
3m the intervertebral foramina.
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1242
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A MANUAL OF ANATOMY
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Branches.—These are as follows: spinal and muscular. T spinal branches enter the vertebral canal through the interverteb: foramina. The muscular branches supply the deep muscles of t neck, and anastomose with the deep cervical, ascending cervical, a occipital arteries.
 +
 +
For the third or suboccipital, and the fourth or intracranial, pai of the vertebral artery, see p. 1151.
 +
 +
Varieties. —(1) The left vertebral artery not uncommonly arises from the ai of the aorta between the origins of the left common carotid and left subclavi arteries. (2) The vessel may pass the foramen transversarium of the sh cervical vertebra, and may enter that of the fifth, or even that of the four (3) The vessel has been found in rare cases to enter the foramen transversarii of the seventh cervical vertebra.
 +
 +
Development. —The vertebral artery is developed from (1) the seventh cervi< somatic artery, and (2) the longitudinal anastomotic chain which connects f seven cervical somatic arteries.
 +
 +
Internal Mammary Artery.—This vessel, so named in contr
 +
 +
distinction to the external mammary, or lateral thoracic, a branch of t second part of the axillary artery, arises from the lower aspect of t' first part of the subclavian very nearly opposite the thyro-cervic trunk. Its course is downwards, forwards, and slightly inwards, ai it disappears behind the sternal end of the clavicle and first cost cartilage. For its subsequent course and relations, see p. 999.
 +
 +
Relations of Cervical Part— Anterior .—The clavicular part of tl sterno-mastoid, and the internal jugular and subclavian veins. Tl phrenic nerve crosses the vessel superficially from without inward Posterior .—The pleura.
 +
 +
No branches arise from this part of the vessel.
 +
 +
Thyro-cervical Trunk (Thyroid Axis).—This is a short trunk whi<; springs from the front of the first part of the subclavian artery clo to the inner border of the scalenus anterior muscle. It almost imm diately divides into three diverging branches—inferior thyroi transverse cervical, and suprascapular.
 +
 +
The inferior thyroid artery passes upwards and inwards in a tc tuous manner in front of the vertebral artery, and behind the carot sheath and sympathetic trunk, the middle cervical ganglion of whit often rests upon it. Having reached the lower part of the lobe of tl thyroid body, the artery breaks up into its terminal branches, whi< enter the lobe on its deep aspect, and ramify in it, anastomosing wi the superior thyroid and with its fellow of the opposite side of tl isthmus. As the vessel ascends it is intimately related to the recurre: laryngeal nerve, which usually lies behind it.
 +
 +
Branches.—These are as follows: muscular, ascending cervic; inferior laryngeal, tracheal, and oesophageal.
 +
 +
The muscular branches supply the scalenus anterior, longus cervic:: the infrahyoid muscles, and inferior constrictor of the pharynx. Tl ascending cervical artery arises from the inferior thyroid as it pass inwards behind the carotid sheath. It ascends in front of the trait verse processes of the cervical vertebrae, lying between the scalenj
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THE HEAD AND NECK
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1243
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rior and longus capitis, and having the phrenic nerve on its outer and the sympathetic trunk just medial to it. It anastomoses branches of the vertebral, occipital, and ascending pharyngeal ries. It may furnish some spinal branches which enter the vertebral il through the intervertebral foramina to be distributed in a manner lar to the other spinal arteries. The inferior laryngeal artery impanies the recurrent laryngeal nerve to the larynx. The tracheal oesophageal branches are distributed as their names suggest, rhe transverse cervical artery passes transversely outwards in t of the scalenus anterior and phrenic nerve, and behind the icular part of the sterno-mastoid, lying a little above the clavicle, also above the suprascapular artery. It then enters the subdan triangle, which it soon leaves by passing deep to the inferior y of the omo-hyoid. It then passes in front of, or between, the ^e-trunks of the brachial plexus to the deep surface of the trapezius $cle. Having reached the anterior border of the levator scapulae, ivides into its two terminal branches—superficial and deep.
 +
 +
The superficial branch [superficial cervical artery) passes superficial the levator scapulae, and is distributed to the trapezius, levator pulae, splenius, and the adjacent lymph glands. The deep branch sterior scapular artery) passes backwards in front of the levator pulae to the superior angle of the scapula. It then descends along base of the bone, under cover of the rhomboid muscles, as far as inferior angle, where it anastomoses with the circumflex scapular 1 subscapular arteries. The artery gives branches to the adjacent iscles, and anterior and posterior branches to the scapula, which
 +
 +
e part in the scapular anastomoses proper (see p. 438).
 +
The deep branch of the transverse cervical is frequently a branch the third part of the subclavian, in which cases there is no transverse vical artery, the superficial branch of the latter artery taking its ice and arising from the thyro-cervical trunk (see p. 1192).
 +
 +
The suprascapular artery passes downwards and outwards in front the scalenus anterior and phrenic nerve, and behind the clavicular rt of the sterno-mastoid. Having reached the back of the clavicle, courses outwards behind that bone, passing in front of the third rt of the subclavian artery and the trunks of the brachial plexus, then passes to the upper border of the scapula in company with the prascapular nerve. For the further course of the vessel and for the
 +
 +
ipular anastomoses of arteries see p. 441.
 +
 +
Branches in the neck are muscular, suprasternal, and nutrient, le muscular branches supply the sterno-mastoid and subclavius. le suprasternal branch descends over the inner end of the clavicle to pply the integument over the manubrium sterni. The nutrient tery of the clavicle is directed outwards, and enters the nutrient
 +
 +
ramen of that bone. It is often double.
 +
 +
Superior Intercostal Artery. —This vessel arises from the second irt of the subclavian on the right side, and from the first part on le left side, in each case from the posterior aspect of the paient
 +
 +
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i 2 4 4
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A MANUAL OF ANATOMY
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 +
 +
trunk. On the right side it is therefore behind the scalenus anter and on the left side close to the inner border of that muscle. ' vessel at first passes backwards and upwards for a short distance, ; then descends in front of the neck of the first rib. At the postei extremity of the first intercostal space it furnishes the first postei intercostal artery to that space, and then descends in front of neck of the second rib to become the second posterior intercom artery. The superior intercostal artery therefore furnishes the fi and second posterior intercostal arteries for the first and second inf costal spaces, their distribution being similar to that of the succeed posterior (aortic) intercostal arteries. Besides these two brand: the vessel gives off the deep cervical artery. This branch, which homologous with the posterior branch of a posterior intercostal arte arises from the superior intercostal before it descends in front of 1 neck of the first rib.
 +
 +
The superior intercostal artery and the deep cervical art< are often described as terminal branches of a common trunk origin. This trunk is called the costo-cervical trunk; in 1 description adopted here this trunk is looked on as part of f superior intercostal itself.
 +
 +
It passes backwards between the transverse process of the sever cervical vertebra and the neck of the first rib, and then ascends betwe the semispinalis capitis and semispinalis cervicis muscles to about f level of the axis. In this situation it anastomoses with the de division of the descending branch of the occipital artery. The de cervical in its course gives off muscular branches which anastomc with branches of the vertebral and ascending cervical arteries, also furnishes a spinal branch which enters the vertebral canal throu the intervertebral foramen between the seventh cervical and fii thoracic vertebrae.
 +
 +
The superior intercostal artery on each side is developed from the anast< motic loop between the upper two or three thoracic somatic arteries.
 +
 +
Subclavian Vein. —This vessel, which is the direct continuation the axillary vein, extends from the outer border of the first rib to t back of the inner end of the clavicle, where it unites with the intern jugular to form the innominate vein. It lies in front of, and on lower plane than, the subclavian artery, and it passes in front of t scalenus anterior muscle and phrenic nerve. In rare cases the ve has been met with passing behind the scalenus anterior. Its princip tributary is the external jugular vein (sometimes also the anteri jugular). The external jugular vein joins it close to the outer bord of the sterno-mastoid.
 +
 +
The thoracic duct opens at the angle of junction of the left su clavian and left internal jugular veins, and the right lymphatic du opens into the angle of junction of the corresponding veins on t] right side. The duct often opens in two or more parts.
 +
 +
Vertebral Vein. —This vein begins in the suboccipital veno
 +
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 +
 +
THE HEAD AND NECK
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 +
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1245
 +
 +
 +
ms within the suboccipital triangle. It passes through the foramen lsversarium in the atlas, and accompanies the vertebral artery nigh the succeeding foramina transversaria as low as the sixth, ning a plexus around the vessel. This plexus is ultimately replaced a single vein, which emerges through the foramen transversarium he sixth cervical vertebra (sometimes the seventh). It then descends ront of the first part of the subclavian artery under cover of the irnal jugular vein, and opens into the back part of the innominate 1, the opening being provided with a single or double valve.
 +
 +
The chief tributaries of the vertebral vein are as follows: muscular, lal, anterior vertebral, and deep cervical. It also, as a rule, dves the first intercostal vein.
 +
 +
No vein accompanies the ceral part of the internal mamry artery. The inferior thyroid a, which does not accompany corresponding artery, is found cribed in connection with the Toid gland on p. 1222.
 +
 +
The transverse cervical and irascapular veins return the od from the parts supplied by i corresponding arteries, and tributaries of the lower part the external jugular vein.
 +
 +
The deep cervical vein starts the suboccipital venous plexus
 +
 +
Tin the suboccipital triangle. ^ 0
 +
 +
descends in company with the Fk, 753-^*^^™ V*™ 'P cervical artery, and passes . , ,, ,•
 +
 +
J xr Anterior jugular frequently opens di
 +
rectly into subclavian vein. Vertebral vein," which receives superior intercostal, opens into beginning of innominate.
 +
 +
 +
 +
INNOM,
 +
 +
 +
wards between the transverse •cess of the seventh cervical tebra and the neck of the first to terminate in the vertebral
 +
 +
 +
rhe anterior vertebral vein begins in a plexus in front of the uppei ical transverse processes. It descends in company with the nding cervical branch of the inferior thyroid artery receiving cular tributaries in its descent, and it opens into the lower part
 +
 +
Jollateral^irculation after Ligature of the Third Part of the Subian Artery.— (i) The suprascapular and the deep branch of the sverse cervical, both branches of the thyro-cervical trunk fiom part of the subclavian, take part in the scapular anastomoses and stomose freely with branches of the first and t rr par s 0 e lary artery. (2) The internal mammary from the first part of subclavian anastomoses with the lateral thoracic from the second
 +
 +
of the axillary.
 +
 +
 +
 +
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1246
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A MANUAL OF ANATOMY
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Collateral Circulation after Occlusion of the First Part of Subclavian Artery. —(1) The vertebral artery of one side anastomc with that of the opposite side. (2) The internal mammary anas moses with the inferior epigastric from the external iliac, and w the posterior intercostal arteries. (3) The inferior thyroid anas moses with the superior thyroid from the external carotid. (4) 1 superior intercostal anastomoses with the third posterior intercosi (5) The deep cervical of the superior intercostal anastomoses with deep division of the descending branch of the occipital from the exter carotid. (6) The scapular branches of the thyro-cervical trr anastomose with branches of the axillary artery. (7) The thora branches of the axillary artery anastomose with the posterior ini costals.
 +
 +
Cervical Part of the Thoracic Duct (Fig. 751). — This part of 1 thoracic duct occupies the root of the neck on the left side, and ] upon the side of the oesophagus, between it and the left subclav: arteries. In this position it ascends to about the level of the sevei cervical vertebra, and then it describes a curve and passes outwar forwards, and downwards in contact with the cupola of the left pleu It then inclines inwards, and, after receiving the left jugular and si clavian trunks, ends in the angle of junction of the internal jugu and subclavian veins of the left side. The terminal orifice of the di is guarded by a valve composed of two segments, which are so direcl as to effectually prevent the reflux of chyle and the flow of blood ii it. The duct crosses the left vertebral artery, passing either in frc of or behind the vertebral vein. In half the cases the duct is dou' for some distance before it enters the internal jugular, and one brar may open into the subclavian vein. Occasionally three or m< openings have been found, and this multiple opening is of surgi importance, for if one branch is cut in an operation on the root of i neck, it is an even chance that there may be another to carry t chyle to the blood-stream. It is important to notice that the di passes behind the vagus and in front of the phrenic nerves.
 +
 +
Right Lymphatic Duct. —The position of this duct corresponds that of the thoracic duct on the left side. It is about inch in lengi and is formed by the union of the right subclavian trunk and rig jugular trunk. Besides returning lymph from the right side of t head and neck and the right upper limb, it receives the lympha vessels from the right side of the heart, the right lung, the upp part of the right half of the thoracic wall, and some of those from t antero-superior surface of the liver. It ends in the angle of juncti of the internal jugular and subclavian veins of the corresponding sic its orifice being guarded by a double valve.
 +
 +
Cervical Portion of the Lung. —The apex of the lung projects in the root of the neck as high as the neck of the first rib. It is cover by the cupola of the pleura, on the inner and anterior aspects of whi the subclavian artery arches outwards. The cupola of the pleura covered by the suprapleural membrane (Sibson’s fascia), which exten
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THE HEAD AND NECK
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1247
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im the medial border of the first rib to the front of the transverse Dcess of the seventh cervical vertebra. This membrane is probably rived from the adjacent scalene muscles, and it may contain some iscular fibres.
 +
 +
 +
The Contents of the Orbit.
 +
 +
The following structures are found in the orbit:
 +
 +
Orbital Fascia. —The periosteum of the orbit is continuous posteriorly th the dura mater through the superior orbital fissure, and constitutes 0 orbital fascia. Anteriorly it becomes continuous with the periinium of the frontal bone, and the periosteum of the maxilla and gomatic bones. Along the supra-orbital and infra-orbital margins 0 superior and inferior palpebral fascia0 blend with it. The orbital >cia is loosely attached to the bony walls of the orbit, and forms a 0ath for the contents of the cavity, which is incomplete in front. Lacrimal Gland. —This gland lies at the anterior and outer part the orbit superiorly, where it occupies the lacrimal fossa on the ler side of the zygomatic process of the frontal bone. It is discaped. Its upper surface is convex, and its under surface is conve in adaptation to the eyeball. The anterior part of the gland is rtly cut off by the outer edge of the levator palpebrae superioris, d is known as the palpebral portion , the chief part being known the orbital portion . The ducts, which issue from both portions, 0 about twelve in number, and they open in a row into the outer part the superior conjunctival fornix.
 +
 +
Blood-supply. —The lacrimal artery.
 +
 +
Nerve-supply. —The lacrimal nerve and sympathetic filaments.
 +
 +
The structure of the gland is something like to that of the parotid. Development. —The lacrimal gland, like the tarsal and ciliary glands, is /eloped as solid epithelial cords from the conjunctiva. These epithelial 'ds spring from the upper and outer part of the conjunctiva, where it is rented from the inner surface of the upper eyelid on to the front of the eyeball, e solid cords grow into the neighbouring mesoderm, and give off lateral proses. Cords and processes, at first solid, soon become hollow, and so give 3 to the alveoli, or acini, and ducts of the lacrimal gland.
 +
 +
In reptiles the ducts open all round the fornix of the conjunctiva, but in unmals only the upper and outer ones persist.
 +
 +
Muscles.— These are the levator palpebrae superioris, rectus superior,
 +
 +
tus inferior, rectus medialis, rectus lateralis, obliquus superior, and
 +
liquus inferior.
 +
 +
Levator Palpebrae Superioris — Origin. —The under surface of the of of the orbit above, in front of, and medial to the optic foramen. Insertion. —By a broad membranous expansion, which divides into ree tendinous laminae. The middle lamina, which is the chief serf ion, and consists largely of involuntary muscular fibres, is attached the upper margin of the superior tarsus. The upper or superficial yer, which is fibrous, passes in front of the superior tarsus, lying tween it and the palpebral fibres of the orbicularis oculi. Its fibres
 +
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1248
 +
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A MANUAL OF ANATOMY
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 +
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pierce the superior palpebral fascia, and, having passed between bundles of the palpebral portion of the orbicularis oculi, they attached to the skin of the upper eyelid. The lower or deep layer , wl is also fibrous, is attached to the conjunctiva along the superior for
 +
 +
 +
Supra-orbital Nerve (in two divisions)
 +
 +
 +
Supratrochlear Nerve Infratrochlear Nerve S™
 +
 +
 +
Olfactory Bulb
 +
 +
 +
Naso-ciliary Nerve
 +
 +
 +
Optic Nerve-
 +
 +
 +
Frontal Nerve on Levator Palpebrae Superioris
 +
 +
Lacrimal Nerve passing along Rectus Lateralis
 +
 +
 +
Ophthalmic Artery’-'
 +
 +
Oculo-motor Nerve"*
 +
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Trochlear Nerve'
 +
 +
Abducent Nerve-'
 +
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Motor Root of Trigeminal Nerve
 +
 +
Fig. 754. —Dissection of the Orbit from above (Hirschfeld and Leveil
 +
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Maxillary Nerve Ophthalmic Nerve 7 Mandibular Nerve '-Trigeminal Ganglion
 +
 +
'•Sensory Root of Trigeminal Nerve
 +
 +
 +
The outer and inner margins of the broad membranous expans are attached to the outer and inner margins of the orbit close to lateral and medial palpebral ligaments, and at the inner angle a < is attached to the pulley of the obliquus superior.
 +
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Nerve-supply .—The 1 per division of the th cranial nerve, the brai from which enters the d< or ocular surface of muscle near its ori£ having pierced the rec superior.
 +
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Action .—To raise upper eyelid. The mus is the antagonist of superior palpebral fibres the orbicularis oculi.
 +
 +
The levator palpebrse is a delamination of the rectus superior, to whicl is so closely attached that, even when it is paralyzed, the upper lid may raised a little by looking upwards.
 +
 +
Relations. — Superiorly , the frontal nerve and the supra-orbi artery. Inferiorly , the rectus superior and the conjunctiva.
 +
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WHICH MOVE THE EYEBALL.
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THE HEAD AND NECK
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1249
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Recti Muscles Rectus Superior— Origin. —The upper part of the rnmon tendinous ring in relation to the optic foramen.
 +
 +
Insertion. By a thin expanded tendon into the upper surface of e sclera about three or four lines from the margin of the cornea. Nerve-supply.-' The upper division of the oculo-motor nerve, the anch from which enters the deep or ocular surface of the muscle ar its origin.
 +
 +
The muscle is flattened from above downwards, and its direction forwards and slightly outwards.
 +
 +
The actions of the muscles of the eyeball are considered together tp- 1251 Relations.' Superiorly , the levator palpebrae superioris, which is e narrower of the two muscles. Inferiorly , the tendon of the obliquus penor, the eyeball, and the soft fat of the orbit.
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Rectus Medialis (Internal Rectus)— Origin. —The inner part of the mmon tendinous ring in relation to the optic foramen, the origin
 +
 +
ing wide.
 +
Insertion. By a thin expanded tendon into the inner surface of e sclera about three or four lines from the margin of the cornea. Nerve-supply. —The lower division of the oculo-motor nerve, the anch from which enters the deep or ocular surface of the muscle.
 +
 +
The muscle is flattened from within outwards, and its borders are perior and inferior. Its direction is almost straight forwards.
 +
 +
Relations.—Above the upper border of the muscle is the obliquus perior, and between the two the naso-ciliary nerve and the anterior id posterior ethmoidal vessels pass.
 +
 +
Rectus Inferior— Origin. —The lower part of the common tendinous ig in relation to the optic foramen.
 +
 +
Insertion. —By a thin expanded tendon into the lower surface the sclera about three or four lines from the margin of the rnea.
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 +
Nerve-supply. —The lower division of the oculo-motor nerve, the anch from which enters the deep or ocular surface of the muscle.
 +
 +
The muscle is flattened from above downwards, and its direction forwards and slightly outwards.
 +
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Relations— Inferior. —A part of the obliquus inferior.
 +
 +
Rectus Lateralis (External Rectus)— Origin. —This muscle arises bv [0 heads. y
 +
 +
Inferior Head.—(1) The lower part of the common tendinous ring relation to the optic foramen, where it is near the rectus inferior; d (2) the prominent spine on the lower margin of the superior orbital sure near its inner end.
 +
 +
Superior Head.—The outer portion of the upper part of the common idinous ring in relation to the optic foramen, where it is above 2 superior orbital fissure, external to the optic foramen, and near - rectus superior. The two heads are connected by a tendinous nd which arches over the superior orbital fissure, and gives origin some of the fibres of the inferior head of the muscle.
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79
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1250
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A MANUAL OF ANATOMY
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Insertion. —The outer surface of the sclera from three to four li from the margin of the cornea.
 +
 +
Nerve-supply. —The abducent nerve, the branches of which en the deep or ocular surface of the muscle.
 +
 +
The muscle is flattened from without inwards, and its directioi forwards and outwards.
 +
 +
Action. —To abduct the eyeball, so as to direct the cornea outwai
 +
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Relations.—The following structures pass between the two he of the muscle in order from above downwards: (i) the upper divis of the oculo-motor nerve; (2) the naso-ciliary nerve; (3) the hr division of the oculo-motor nerve; (4) the abducent nerve; and (5) superior ophthalmic vein or veins.
 +
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Common Tendinous Ring of the Recti Muscles.—This tendon ta the form of a fibrous ring, which is attached to the upper, inner, ; lower margins of the optic foramen. It then crosses transvers the inner portion of the superior orbital fissure to a prominent sp on the lower margin of that fissure near its inner end. From 1 spine it recrosses the superior orbital fissure in a vertical direct near its centre, and finally reaches the upper part of the optic foram This latter portion gives origin to some fibres of the inferior head the rectus lateralis. The upper part of the ring is sometimes knc as the tendon of Lockwood , and gives origin from within outwa to part of the rectus medialis, the rectus superior, and the supei head of the rectus laterals. The lower part is also sometimes ca]
 +
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the ligament of Zinn y which gives ori from within outwards to part of the rec medialis, the rectus inferior, and the infei head of the rectus lateralis.
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Obliqui Muscles — Obliquus Superio: Origin. —The wall of the orbit directly front of the upper and inner part of optic foramen, close to the recti superio] medialis.
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 +
Insertion. —By an expanded tendon i the upper and outer aspect of the sc] just beyond the outer border of the supe: rectus, and midway between the margir the cornea and the entrance of the oj nerve.
 +
 +
The muscle is situated at the upper 1 inner part of the orbit, internal to levator palpebrae superioris. It is directed forwards towards inner angle of the orbit, on approaching which it ends in a sr round tendon. This tendon passes through a fibro-cartilagin pulley close to the medial angular process of the frontal bone, then changes its direction, and passes downwards, outwards, ; backwards beneath the tendon of the rectus superior to reach insertion just lateral to that tendon.
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Fig. 756.—The Superior Oblique Muscle.
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THE HEAD AND NECK
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1251
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The fibro-cartilaginous pulley or trochlea is attached by fibrous
 +
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sue to the trochlear fossa on the orbital plate of the frontal bone
 +
)se to the medial angular process. It is lined with synovial membrane lubricate the tendon and facilitate its movement at this abrupt ange in its course. The tendon receives a fibrous investment from e outer margin of the pulley.
 +
 +
Nerve-supply.—The trochlear nerve, which enters the muscle on
 +
 +
superficial or orbital surface near its origin.
 +
Relations— Superior. —The roof of the orbit and the rectus superior. ferior. —The upper border of the rectus medialis, having the nasoiary nerve and the anterior and posterior ethmoidal vessels between em. Lateraf^—-The levator palpebrae superioris.
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Obliquus Snpemr — Origin. —A small depression at the anterior and tier part of the floor of the orbit immediately lateral to the upper >ening of the lacrimal canal.
 +
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Insertion. —The outer surface of the sclera under cover of the rectus teralis, and slightly posterior to the level of the insertion of the iliquus superior.
 +
 +
Nerve-supply— The lower division of the oculo-motor nerve, the anch of which is long and enters the posterior border of the muscle. The muscle at first passes outwards and backwards upon the floor the orbit beneath the rectus inferior, and then it turns upwards itween the sclera and the rectus lateralis, where its tendon expands lore its insertion.
 +
 +
Relations. —Towards the eyeball the muscle is related to the ctus inferior and the sclera, and towards the orbit to the floor of e cavity and the rectus lateralis. The borders of the muscle are Lterior and posterior, the latter, as stated, receiving the nerve ppiy Movements of the Eyeball. —The movements of the eyeball con>t of rotation round a point situated just behind the centre of its hero-posterior axis. When the eyeball rotates round its vertical
 +
 +
is, horizontal or lateral movements take place, and the cornea
 +
directed outwards or inwards according to the muscle which acts. ie rectus lateralis abducts the eyeball, so as to direct the cornea itwards, and the rectus medialis adducts the eyeball, so as to rect the cornea inwards. When the eyeball rotates round its trans;rse axis vertical or upward and downward movements take place, id the cornea is directed upwards or downwards according to the uscle which acts. The rectus superior elevates the eyeball, and e rectus inferior depresses it. It is to be borne in mind, however, at these two muscles in passing forwards have each a slight innation outwards. Whilst, then, they respectively elevate and depress e cornea on the transverse axis of the eyeball, each of them also ^es it a certain amount of inward movement on the vertical axis, companied by slight rotation on the antero-posterior axis. In e case of the rectus superior this inward and rotatory movement corrected by the obliquus inferior acting in association with it, and
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1252
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A MANUAL OF ANATOMY
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in the case of the inferior rectus by the obliquus superior acting association with it.
 +
 +
Direct elevation of the eyeball is therefore effected by the re< superior, aided by the obliquus inferior, and direct depression of eyeball is effected by the rectus inferior, aided by the obliquus supei The superior oblique, acting alone, would depress the cornea abduct it, making the eye look downwards and outwards, and obliquus inferior, acting alone, would elevate and abduct it, tl movements in each case being accompanied by slight rotation on antero-posterior axis.
 +
 +
Fascia of the Orbit.—This fascia forms (i) the fascial sheath
 +
 +
 +
the eyeball, fascia bulbi; and (2) sheaths for the ocular muscles.
 +
 +
The fascia bulbi is practically the thickened wall of a lyn space round the sclerotic coat of the eyeball, and extends from
 +
 +
point of entrance of the o]
 +
 +
 +
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nerve to near the margin of cornea. Posteriorly it is perfora by the ciliary vessels and ner and blends with the dura ma sheath of the optic nerve, ; anteriorly it fades away when meets the ocular conjunctiva, outer surface of the capsule h contact with the orbital fat, ; anteriorly with the ocular c junctiva. The fascial sheath (c sule of Tenon) forms a cavity socket, within which the eyel glides with perfect freedom fr friction.
 +
 +
The lower part of the fas< sheath of the eyeball is said to thickened by the suspensory li ment of the eye (Lockwood). This is attached laterally to Whitna tubercle on the zygomatic bone, and medially to the lacrimal bo It is expanded beneath the eyeball, to the fore part of which it a as a sling or support.
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The muscular sheaths are derived from the fascial sheath of eyeball. The tendons of the six ocular muscles pierce the fas( sheath on their way to their insertions, which latter are under cover the fascial sheath, each muscle receiving a prolongation from the mar ; of the cleft in the sheath through which its tendon passes. Th prolongations extend backwards around the muscles, and ultimat blend with their perimysial sheaths. As regards the obliquus super muscle, the prolongation around its tendon extends upwards, inwar and forwards as far as the margin of the pulley, to which it is attach The prolongation around the tendon of the obliquus inferior mus extends downwards as far as the outer part of the floor of the orbit
 +
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 +
It has an endothelial lining (dotted line) which is reflected along the tendons to their insertions; the fibrous basis is reflected back towards the muscle.
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THE HEAD AND NECK
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1253
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The sheaths of the four recti muscles give off important expanms. The expansion from the sheath of the rectus lateralis is strong, id is attached to the frontal process of the zygomatic bone, and at from the sheath of the rectus medialis, also strong, is attached the lacrimal crest of the lacrimal bone. These two expansions their bony attachments are connected with the lateral extremities the suspensory ligament of the eye. The expansion from the eath of the rectus superior blends with the deep layer of the tendon the levator palpebrae superioris, and that from the sheath of the
 +
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tus inferior is connected with the inferior tarsus. These expansions
 +
>m the sheaths of the recti, especially from those of the recti lateralis medialis, moderate the action of the muscles, and the latter two e hence known as the check ligaments.
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Nerves in the Orbit—Optic Nerve.—The optic nerve extends forirds and outwards from the optic chiasma, and enters the orbit rough the optic foramen, having the ophthalmic artery below it first, and then on its outer side. It receives sheaths from the ira mater and arachnoid, the former being strong, and at its entrance to the orbit it is surrounded by the origins of the four recti muscles.
 +
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? direction is forwards and outwards, with a slight inclination wnwards, to the back part of the eyeball, where it pierces the sclera out inch medial to, and a little below, the centre. It then pierces e choroid coat, and ends in the nerve-fibre layer of the retina. The iary ganglion is close to the outer side of the nerve towards the back rt of the orbit, and in front of this the nerve is surrounded by the iary nerves and vessels. It is crossed superiorly by the ophthalmic tery, the superior ophthalmic vein, and the naso-ciliary nerve, feriorly, about J inch behind the eyeball, the central artery of the tina enters it and then runs forward within it to the retina.
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Third or Oculo-motor Nerve.—This nerve, having left the outer dl of the cavernous sinus, breaks up at the superior orbital fissure into 0 divisions, upper and lower. These enter the orbit between the 0 heads of the rectus lateralis muscle, the naso-ciliary nerve being uated between the two.
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 +
The superior division enters the deep surface of the rectus superior pplying it, after which it pierces the muscle and ends in the levator lpebrae superioris.
 +
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The inferior division, larger than the upper, has three branches, lich supply the rectus medialis, the rectus inferior, and the obliquus hrior. The twigs to the recti medialis et inferior enter these muscles their deep or ocular surfaces. The branch to the obliquus inferior a long nerve which passes forwards between the recti inferior et eralis, and its twigs enter the obliquus inferior muscle at its posterior 'der. Posteriorly it furnishes the ganglionic branch, which forms the 3 rt or parasympathetic root of the ciliary ganglion.
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The fourth, trochlear, or pathetic nerve, of small size, having left 2 wall of the cavernous sinus, enters the orbit through the superior sital fissure above the muscles, and medial to, but on a slightly
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I2 54
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A MANUAL OF ANATOMY
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higher plane than, the frontal nerve. Having passed inwards o 1 the levator palpebrae superioris, it enters the posterior part of the ol quus superior muscle on its superficial or orbital surface, this bei the only muscle which it supplies.
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The sixth or abducent nerve, having left the cavernous sinus, ent the orbit through the superior orbital fissure, and passes between 1
 +
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two heads of the rectus lateralis muscle, this situation it has the lower division of 1 oculo-motor nerve above it, and the super ophthalmic veins below it. It supplies 1 rectus lateralis, its twigs entering the mus on its deep or ocular surface.
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Branches of the Ophthalmic Division of I Trigeminal Nerve. — The ophthalmic ner having left the outer wall of the cavernc sinus, and before reaching the superior orbi fissure, divides into frontal, lacrimal, a naso-ciliary nerves.
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The frontal nerve, of large size, enters 1 orbit through the superior orbital fissure abc the muscles. In this situation it has the 1; rimal nerve lateral to, and on the same pla with it, and the trochlear nerve medial to but on a slightly higher plane. It then pas: forwards on the upper surface of the levai palpebrae superioris, underneath the periostei of the roof of the orbit, and before arrivi at the supra-orbital margin it divides into t branches, supra-orbital and supratrochlear.
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The supra-orbital nerve, which in size a direction is the continuation of the front passes forwards to the supra-orbital notch foramen, through which it leaves the orbit company with the supra-orbital artery. ( the forehead it divides into two branches, late and medial, which have been already descrit (see p. 1153). Sometimes this division takes place within the ort and in these cases the inner branch usually passes through the sup: orbital notch.
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The supratrochlear nerve, of small size, passes forwards and inwai to the pulley to the obliquus superior muscle, above which it runs the forehead, where it has been already described (see p. 1154)- Bef( leaving the orbit it gives off a small twig, which passes downwar close to the pulley of the obliquus superior, to form a loop with i infratrochlear branch of the naso-ciliary nerve.
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The lacrimal nerve enters the orbit through the superior orbi fissure above the muscles, and external to the frontal nerve. It tt passes forwards and outwards along the upper border of the rec
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Fig. 758. —The Third and Sixth Cranial Nerves in the Orbit .
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I.O., nerve to inferior oblique; other branches running directly forward from lower division of the third nerve are going to inferior rectus.
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THE HEAD AND NECK
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1255
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eralis in company with the lacrimal artery. On reaching the lacrimal
 +
md it gives numerous branches to its deep surface, and is then coniued through the orbital septum to the skin and conjunctiva of the ter part of the upper eyelid, and the skin in the region of the zygoitic process of the frontal bone. Near the lacrimal gland it sends wnwards a small twig, which joins the zygomatico-temporal nerve. The naso-ciliary nerve (nasal nerve) is more deeply placed than the rntal and lacrimal. It enters the orbit through the superior orbital sure, and passes between the two heads of the rectus lateralis muscle, [ng between the upper and lower divisions of the oculo-motor nerve, then passes obliquely inwards and forwards to the inner wall of the bit, lying beneath the rectus superior and above the optic nerve, d, later on, between the obliquus superior and the rectus medialis. iving reached the inner wall of the orbit at the anterior ethmoidal
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g. 759- —Scheme of the Distribution of the Oculo-motor, Trochlear,
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and Abducent Nerves (Flower).
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f U - D - { L rJ: Sg2£sSKZ" SUPeri ° riS
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! rR.Int. Rectus Medialis
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Oculo-Motor Nerve ' L.D. Lower Division -j R.Inf. Rectus Inferior
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( O.I. Obliquus Inferior
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C.G. Ciliary Ganglion ^ M.R. Motor Root
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S.R. Sensory Root (from Naso-ciliary Nerve) Sy.R. Sympathetic Root S.C. Short Ciliary Nerves Trochlear Nerve—O.S. Obliquus Superior Abducent Nerve—R.E. Rectus Lateralis.
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ramen, it parts with its infratrochlear branch, and then passes through e foramen in company with the anterior ethmoidal artery, and so iters the anterior fossa of the base of the skull. It then passes forwards id inwards in a groove on the upper surface of the cribriform plate the ethmoid bone, lying under cover of the dura mater. Having ached the nasal slit at the side of the fore part of the crista galli, descends through this slit, or through a small foramen just in front it, into the nasal cavity, and immediately gives off two internal nasal anches. Then the nerve descends in a groove on the posterior surface the nasal bone, giving offsets to the mucous membrane of the outer all of the nasal cavity in front of the superior and middle nasal •nchae. Finally, the nerve comes out, as the external nasal branch, dween the lower border of the nasal bone and the upper nasal cartilage, id supplies the skin of the tip and lower part of the side of the nose.
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A MANUAL OF ANATOMY
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1:256
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In connection with this remarkable course of the nerve it is to t noted that it is to be met with in four different regions—name! (1) in the orbit; (2) on the cribriform plate of the ethmoid bone : the anterior cranial fossa; (3) in the nasal cavity; and (4) on the fa< in the region of the tip of the nose.
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Branches. —The ramus communicans to the ciliary ganglion forms tl long or sensory root of that ganglion. It is slender, about ^ inch Ion and arises from the naso-ciliary as it passes between the two hea( of the rectus lateralis. It enters the ciliary ganglion at its poster superior angle.
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The long ciliary nerves , usually two in number, arise from tl naso-ciliary immediately after it has crossed the optic nerve, and the
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Supra-orbital Nerve (in two divisions)
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Supratrochlear Nerve—: In fra trochlear Naso-ciliary—'
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Olfactory Bulb Naso-ciliary Nerved
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Optic Nerve—
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?
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Ophthalmic Artery — Oculo-motor Nerve- - """
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Trochlear Nerve
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-•Frontal Nerve on Levator Palpebrae Superioris
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• Lacrimal Nerve passing along
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Rectus Lateralis
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~ Maxillary Nerve Ar Ophthalmic Nerve
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Mandibular Nerve
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'.Trigeminal Ganglion
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Abducent Nerve"' j ,,v ‘ Sensory Root of Trigeminal Nerve
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Motor Root of Trigeminal Nerve
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Fig. 760. —Dissection of the Orbit from above (Hirschfeld and
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Leveille) .
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communicate with the short ciliary nerves from the ciliary ganglioi which they accompany to the back part of the sclera. Here they pierc the sclera, and are distributed along with the short ciliary nerves.
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The infratrochlear nerve arises from the naso-ciliary close to th anterior ethmoidal foramen, and passes forwards beneath the obliqur superior muscle. Near the pulley of that muscle it receives a twi from the supratrochlear nerve, and then, passing beneath the puller it leaves the orbit at the medial angle to be distributed to the ski and conjunctiva of the inner parts of the eyelids, the side of the roc of the nose, the lacrimal sac, and the caruncula lacrimalis.
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As the nerve traverses the anterior ethmoidal canal it gives twig to the mucous membrane of the frontal sinus and of the anterior etl moidal sinus.
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THE HEAD AND NECK
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1257
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A posterior ethmoidal nerve is described as passing through the isterior ethmoidal canal to supply the mucous membrane of the jsterior ethmoidal sinus and of the sphenoidal sinus.
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For the branches of the naso-ciliarv nerve to the exterior of the nose id to the nasal fossa, see p. 1276.
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Ciliary Ganglion (Lenticular Ganglion).—This is a small quadriteral body, about the size of a moderately large pin-head, which is
 +
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uated in the posterior part of the orbit, where it lies flattened upon
 +
e outer side of the optic nerve. It is usually in close contact with
 +
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A
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Fig. 761.—A, The Ciliary Ganglion; B, The Nerves of the Orbit (Lateral Aspect) (Hirschfeld and Leveille).
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lternal Carotid Plexus phthalmic Nerve aso-ciliary Nerve ympathetic Root of Ciliary Ganglion
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rigeminal Ganglion 'culo-motor Nerve bducent Nerve lternal Carotid Artery ptic Nerve
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ommon Tendinous Ring for Recti
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A
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5. Sensory Root of Ciliary Gang lion
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6. Long Ciliary Nerves
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7. Branch of Oculo-motor Nerve
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to Obliquus Inferior
 +
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B
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7. Levator Palpebrae Superioris
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8. Rectus Superior
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9. Frontal Nerve
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10. Rectus Lateralis
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11. Obliquus Superior
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12. Rectus Inferior
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13. Short Ciliary Nerves
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8. Motor Root of Ciliary Ganglion
 +
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9. Ciliary Ganglion
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10. Infratrochlear Branch of Naso ciliary Nerve
 +
 +
11. Short Ciliary Nerves
 +
 +
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14. Branch of Oculo-motor Nerve to
 +
 +
Obliquus Inferior
 +
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15. Ciliary Ganglion
 +
 +
16. Ophthalmic Nerve
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17. Maxillary Nerve
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 +
18. Mandibular Nerve
 +
 +
 +
it nerve, and is recognized by its reddish-pink colour. Posteriorly receives its three roots, and anteriorly the short ciliary nerves pass wards from it. The roots are called sensory, motor, and sympathetic, e sensory root is derived from the naso-ciliary nerve as it passes
 +
 +
ween the two heads of the rectus lateralis. It is slender, about
 +
nch long, and enters the postero-superior angle of the ganglion, e motor root is derived from the long branch of the lower division the oculo-motor nerve which supplies the obliquus inferior muscle, 1 it enters the postero-inferior angle of the ganglion. The sym
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1258
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A MANUAL OF ANATOMY
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pathetic root is a very minute nerve which is derived from the interi carotid plexus of the sympathetic, and it usually reaches the gangli in company with the sensory root. It may, however, join the gangli separately, and then it does so in close proximity to the entrance the long root.
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The branches of the ciliary ganglion are called the short cilic, nerves. They are from six to eight in number, and come off in b groups from the antero-superior and antero-inferior angles. T nerves of the lower group usually exceed those of the upper in numb As they pass forward above and below the optic nerve they divide, a give rise to from sixteen to twenty delicate filaments. Having reach the back of the eyeball, they pierce the sclera around the entrar of the optic nerve. They then pass forwards between the sclera a
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Infratrochlear Artery Medial Palpebral Arteries
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Dorsal Nasal Artery-— Pulley of Obliquus Oblique-.
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Anterior Ethmoidal Artery.
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Posterior Ethmoidal Artery..
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Central Artery of the Retina (in outline)
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Obliquus Superior Rectus Superior (cut)
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Levator Palpebra? Superioris (cut)
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Optic Nerve Optic Chiasma (right half)
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Lacrimal Gland
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Supra-orbital Artery
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Long Posterior Ciliary Arteries
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Lacrimal Artery
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Rectus Lateralis (cut) Ophthalmic Artery
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Right Optic Tract
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Fig. 762. —Dissection of the Right Orbit from above, showing the Op Nerve, Ophthalmic Artery, and Superior Oblique Muscle.
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the choroid, giving twigs to the latter, and they are finally distribul to the ciliary muscle, the iris, and the cornea. The short cilic nerves thus convey co the eyeball sensory fibres from the ophthalr division of the trigeminal nerve, motor fibres from the oculo-mo nerve, and sympathetic fibres from the internal carotid plexus of 1 sympathetic.
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Summary of the Ophthalmic Nerve. —This nerve is entirely sensory, supplies (1) the skin of (a) the frontal region and top of the skull; (&) the up eyelid, and (c) the root, tip, and lower part of the side of the nose; (2) the cari cula lacrimalis and lacrimal sac; (3) the mucous membrane of the nasal cavi and the conjunctiva; (4) the eyeball; and (5) the lacrimal gland.
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Summary of the Ciliary Ganglion. —The branches of this ganglion supply 1 cornea, iris, and ciliary muscle. The fibres which supply the sphincter pUpi are derived from the oculo-motor nerve by means of the motor root of the gangli
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THE HEAD AND NECK
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1259
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le fibres which supply the dilator pupillse are derived from the sympathetic by eans of the sympathetic root of the ganglion, which is derived from the internal rotid sympathetic plexus.
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Branch of the Maxillary Division of the Trigeminal Nerve.—The rgomatic nerve (temporo-malar nerve), of small size, arises from the axillary in the pterygo-palatine fossa. It enters the orbit through Le inferior orbital fissure, and soon divides into two branches, zygoatico-temporal and zygomatico-facial. The zygomatico-temporal nerve imp oral branch) ascends upon the outer wall of the orbit, and, having ceived a communicating twig from the lacrimal nerve, it leaves the ivity by passing through the zygomatico-temporal canal in the rgomatic bone. Its destination is the skin of the anterior part of Le temporal region.
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Medial Palpebral Arteries Supratrochlear Artery
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Dorsal Nasal Artery
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Anterior Ethmoidal Artery
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Posterior Ethmoidal Artery Ophthalmic Artery
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Posterior Ciliary Arteries Ophthalmic Artery (in Optic Foramen)
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Lacrimal Gland
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-\ Lateral Palpebral . j Arteries
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Supra-orbital Artery
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Lacrimal Artery
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- Muscular Arteries Arteria Centralis Retinae '■ Posterior Ciliary Arteries
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— Internal Carotid Artery
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Fig. 763. —Diagram of the Ophthalmic Artery and its Branches.
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The zygomatico-facial nerve [malar branch ) passes forwards in the lgle between the outer wall and floor of the orbit, and leaves the vity by passing through the zygomatico-facial canal, from which comes out through the corresponding foramen. It is distributed 1 the skin over the zygomatic bone.
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Ophthalmic Artery.—This vessel arises from the internal carotid tery on the inner aspect of the anterior clinoid process, and enters e orbit through the optic foramen, lying beneath the optic nerve, ithin the orbit it is situated for a short distance on the outer side the optic nerve, and then it passes obliquely inwards and forwards a tortuous manner over the nerve to the inner wall of the orbit, len it passes forwards to the region of the medial angular process the frontal bone, near which it divides into its three terminal branches dorsal nasal, supratrochlear, and palpebral.
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I26o
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A MANUAL OF ANATOMY
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Branches. —These are as follows:
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1. Central artery of the retina.
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2. Posterior ciliary.
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3. Lacrimal.
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4. Muscular.
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5. Supra-orbital.
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6. Posterior ethmoidal.
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7. Anterior ethmoidal.
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8. Palpebral (two), g. Nasal.
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10. Frontal.
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The central artery of the retina (arteria centralis retinae) aris from the ophthalmic at the back part of the orbit below the opt nerve. Its direction is forwards beneath the nerve, and at a poii about \ inch behind the eyeball it enters the nerve, and passes forwan in its centre to the retina, upon which it ramifies. It must be unde stood that this is the only blood-supply of the retina, and that i obliteration means blindness of the eye to which it goes; it is therefor in spite of its small size, one of the most important arteries in the bod;
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The posterior ciliary arteries arise from the ophthalmic whilst is below the optic nerve. They are arranged in two sets, lateral an medial, which pass forwards on either side of the optic nerve to the bac part of the eyeball. Here they pierce the sclera, and the majorit of them enter the choroid coat under the name of the short postern ciliary arteries. Two of them, however, are fairly large, and are know as the long posterior ciliary arteries. They pass forwards betwee the sclera and the choroid, one on each side, and are distributed 1 the ciliary muscle and iris.
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The lacrimal artery arises from the ophthalmic on the outer sic of the optic nerve, and passes forwards along the upper border of tl rectus lateralis muscle to the lacrimal gland. In its course it furnish* the following branches: (1) a recurrent meningeal branch, whic passes through the outer part of the superior orbital fissure to tl middle cranial fossa, where it anastomoses with the middle meninge; artery; (2) muscular and anterior ciliary branches, the latter piercir the sclera very near the corneal margin; (3) zygomatic offsets, whic pass through the zygomatico-temporal and zygomatico-facial canals ( the zygomatic bone to the face and temporal region in company wit the respective branches of the temporo-zygomatic nerve; (4) tw lateral palpebral arteries, superior and inferior, which pass inwarc in the upper and lower eyelids, and anastomose with the medi; palpebral branches of the ophthalmic, thus forming arterial arches and (5) glandular branches to the lacrimal gland.
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