Head Development

Embryology - 1 Dec 2023        Expand to Translate
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Introduction

Fetal head (week 12)

The head and neck is not really a "system", but structurally quite different in origin from the body. The head and neck are one of the most complicated structures that the embryo forms, with special intermediate structures (the pharyngeal arch) and contributions from all 3 embryonic layers (ectoderm, mesoderm, endoderm), and significantly, a major contribution from the neural crest. Neural crest contributes jaw skeletal elements, connective tissues and tendons. The associated muscles derive mainly from cranial mesoderm. These components though will form different structures dependent upon which arch they are within. The cavity within the pharyngeal arches forms the pharynx.

The pharynx contributes to 2 endocrine organs, in the roof the pituitary (hypophysis) and the floor the thyroid. The thyroid gland, being one of the first endocrine organs to be formed, has an important role in embryonic development. The pharynx floor of all arches also contribute to the formation of the tongue.

Because the head contains many different structures also review notes on: skull, sensory (placode, vision, hearing, smell, taste), respiratory (pharynx), integumentary(tooth, hair) and endocrine (pituitary, thyroid, parathyroid, thymus).

Some Recent Findings

Review - MR Imaging of the Fetal Face "The human face is a complex anatomic structure with an equally complex embryologic development. Derangement of the developmental process can result in various structural anomalies, which range from a mainly cosmetic deformity, such as cleft lip, to potentially life-threatening conditions such as arhinia. These anomalies (a) can occur as isolated anomalies; (b) can be associated with intracranial, spinal, or dental anomalies; or (c) can be a part of various syndromes, thus serving as diagnostic clues in such cases. Proper evaluation of fetal facial deformities can help in prognostication, family counseling, and prenatal or early postnatal intervention. Ultrasonography (US) is the first line of investigation in these cases. However, when US does not allow complete evaluation of these anomalies owing to its inherent limitations, magnetic resonance (MR) imaging allows comprehensive evaluation of the anomaly itself and also evaluation of various associations and the treatment approach. The embryology of the fetal facial structures is considered with regard to the MR imaging technique and the MR imaging anatomy. The MR imaging features of various structural anomalies are described and classified into six groups, namely, orofacial clefts, orbital anomalies, nasal anomalies, facial masses, external ear anomalies, and abnormal face shape or profile." Magnetic Resonance Imaging Branchial anomalies in children: A report of 105 surgical cases "Branchial anomalies (BAs) account for 20% of all congenital masses in children. We sought to review the incidence of involvement of individual anomalies, diagnostic methods, surgical treatment, and complications of BAs in children. ...A total of 33 (31.4%) cases presented with first BAs, 13 (12.4%) presented with second BAs, and 59 (56.2%) presented with third and fourth BAs, including 6 cases of congenital lower neck cutaneous fistula."

More recent papers

This table allows an automated computer search of the external PubMed database using the listed "Search term" text link. This search now requires a manual link as the original PubMed extension has been disabled. The displayed list of references do not reflect any editorial selection of material based on content or relevance. References also appear on this list based upon the date of the actual page viewing. References listed on the rest of the content page and the associated discussion page (listed under the publication year sub-headings) do include some editorial selection based upon both relevance and availability. More? References | Discussion Page | Journal Searches | 2019 References | 2020 References Search term: Head Development | Pharyngeal Arch Development | Skull Development | Face Development |

Older papers

These papers originally appeared in the Some Recent Findings table, but as that list grew in length have now been shuffled down to this collapsible table. See also the Discussion Page for other references listed by year and References on this current page. Developmental and evolutionary origins of the pharyngeal apparatus "The vertebrate pharyngeal apparatus, serving the dual functions of feeding and respiration, has its embryonic origin in a series of bulges found on the lateral surface of the head, the pharyngeal arches. Developmental studies have been able to discern how these structures are constructed and this has opened the way for an analysis of how the pharyngeal apparatus was assembled and modified during evolution. For many years, the role of the neural crest in organizing pharyngeal development was emphasized and, as this was believed to be a uniquely vertebrate cell type, it was suggested that the development of the pharyngeal apparatus of vertebrates was distinct from that of other chordates." hand2 and Dlx genes specify dorsal, intermediate and ventral domains within zebrafish pharyngeal arches. "The ventrally expressed secreted polypeptide endothelin1 (Edn1) patterns the skeleton derived from the first two pharyngeal arches into dorsal, intermediate and ventral domains. ...Collectively, our work indicates that the expression and function of hand2 and Dlx genes specify major patterning domains along the dorsoventral axis of zebrafish pharyngeal arches."

Textbooks

• The Developing Human: Clinically Oriented Embryology (8th Edition) by Keith L. Moore and T.V.N Persaud - Moore & Persaud Chapter Chapter 10 The Pharyngeal Apparatus pp201 - 240.
• Larsen’s Human Embryology by GC. Schoenwolf, SB. Bleyl, PR. Brauer and PH. Francis-West - Chapter 12 Development of the Head, the Neck, the Eyes, and the Ears pp349 - 418.

UNSW Students
	You have access the following online Embryology textbooks through the UNSW Library.
	Moore, K.L. & Persuad, T.V.N. (2008). The Developing Human: clinically oriented embryology (8th ed.). Philadelphia: Saunders. The following chapter links only work with a UNSW connection. Chapter 9 Pharyngeal Apparatus, Face, and Neck Chapter 18 Development of Eyes and Ears

Objectives

• List the main structures derived from the pharyngeal arches, pouches and clefts.
• Know the stages and structures involved in the development of the face.
• Predict the results of abnormal development of the face and palate.
• Briefly summarise the development of the tongue.

The Pharynx

The cavity within the pharyngeal arches forms the pharynx.

The pharynx contributes to 2 endocrine organs, in the roof the [endocrine7.htm pituitary] (hypophysis) and the floor the thyroid. The thyroid gland being one of the first endocrine organs to be formed has an important role in embryonic development. The pharynx floor of all arches also contribute to the formation of the [head6.htm tongue].

Pharyngeal Arch Components

Human embryo pharyngeal arches (Stage 13 oral cavity floor)

Major features to identify for each: arch, pouch, groove and membrane. Contribute to the formation of head and neck and in the human appear at the 4th week. The first arch contributes the majority of upper and lower jaw structures.

Early Face and Pharynx

• Pharynx - begins at the buccopharyngeal membrane (oral membrane), apposition of ectoderm with endoderm (no mesoderm between)

Pharyngeal Arch Development

• branchial arch (Gk. branchia= gill)
• arch consists of all 3 trilaminar embryo layers
• ectoderm- outside
• mesoderm- core of mesenchyme
• endoderm- inside

Neural Crest

• Mesenchyme invaded by neural crest generating connective tissue components
• cartilage, bone, ligaments
• arises from midbrain and hindbrain region

Arch Features

Each arch contains: artery, cartilage, nerve, muscular component

Arches and Phanynx Form the face, tongue, lips, jaws, palate, pharynx and neck cranial nerves, sense organ components, glands

• Humans have 5 arches - 1, 2, 3, 4, 6 (Arch 5 does not form or regresses rapidly)
• from in rostro-caudal sequence, Arch 1 to 6 from week 4 onwards
• arch 1 and 2 appear at time of closure of cranial neuropore

• Face - mainly arch 1 and 2
• Neck components - arch 3 and 4 (arch 4 and 6 fuse)

Arch Features

• • arch
  • groove
    • externally separates each arch
      • also called a cleft
    • only first pair persist as external auditory meatus
  • pouch
    • internally separates each arch
    • pockets from the pharynx
  • membrane
    • ectoderm and endoderm contact regions
    • only first pair persist as tympanic membrane
• Pharyngeal Arch 1 (Mandibular Arch) has 2 prominances
  • smaller upper- maxillary forms maxilla, zygomatic bone and squamous part of temporal
  • larger lower- mandibular, forms mandible
• Pharyngeal Arch 2 (Hyoid Arch)
  • forms most of hyoid bone
• Arch 3 and 4
  • neck structures

Arch Arteries

Arch 1 - mainly lost, form part of maxillary artery Arch 2 - stapedial arteries Arch 3 - common carotid arteries, internal carotid arteries Arch 4 - left forms part of aortic arch, right forms part right subclavian artery Arch 6 - left forms part of left pulmonary artery , right forms part of right pulmonary artery placental vein -> liver -> heart -> truncus arteriosus -> aortic sac -> arch arteries -> dorsal aorta -> placental artery

Human embryo (5mm, lateral view) showing pulmonary arteries

Arch 5 Artery?
There has been ongoing controversy as to whether the fifth arch artery, that forms in fish, ever develops in birds and mammals. A recent study in mouse and human embryos identified the presence of an extra vessel presence in a single Carnegie Stage 14 human embryo.

Congdon (1922) Table 1

Table 1. Showing correlation of size of embryos and development of the aortic-arch system. Embryo No. Length in mm. Arches present. Characteristic features. Time of establishment of first arch; estimated average length 1.3 mm.; 23d day of development 1878 1.3 I Slightly plexiform. Presomite stage 1201 2 I 391 2 I 7 somites 470 4 I Neuropores open; 14 to 16 somites 2053 3 I; II beginning Anterior neuropore closed; 20 somites; transverse anastomoses between primitive aortae Template:CE1201b 3 I. II Earlier mandibular aitery; paired longitudinal neural arteries; 836 4 II, III no ventral tract on cord Just before establishment of fourth arch; estimated average length 4 mm.; 31st day of development 826 5 III, IV Earlier mandibular and hyoid arteries 1075 6 III, IV Subclavian 588 4 III, IV Earlier mandibular and hyoid arteries 873 6 III, IV Ventral arterial tract on cord 988 6 III, IV 1380 4 III, IV, pulmonary arches almost complete 2841 4 III, IV; one so-called fifth arch; pulmonary almost complete Early formation of basilar artery Just before completion of pulmonary arch; estimated average length 6 mm.; 36th day of development 810 5 III, IV, and pulmonary arches Late stage in formation of basilar artery, Splitting of aortic sac distinct. Unpaired aorta complete 1354 6 III, IV, and pulmonaiy arches 617 7 III, IV, two so-called fifth arches, and pulmonary arches Subclavian artery surrounded by brachial plexus. Splitting of sac well marked. Islands at end of basilar artery 792 8 III, IV, and pulmonary arches Pulmonary and IV arches widely separated below 1121 11 III, IV, and pulmonary arches Right pulmonary artery small; basilar rounded; IV and pulmonary still farther apart 721 9 III, IV, and pulmonary arches Cervical segmental arteries becoming interrupted 163 9 III, IV, and pulmonary arches Anastomoses of cervical segmental arteries to form the vertebral artery are nearly complete Time of interruption of pulmonary arch and of branchial period; estimated average length 12 mm 45th day of development 1771 13 III, IV, left pulmonary and remnant of right pulmonary arch 544 10 Vertebral artery complete; identity of arches disappearing; beginning of period of rapid descent of heart and arteries 940 14 Definitive aortic arch just taking form. Right dorsal aorta between III and IV interrupted. Remnants still distinguishable. Main pulmonary channel from heart to aorta nearly straight 1909 15 Common carotid elongated 492 16 Right dorsal aorta distal to IV patent but slender Template:CE74 16 End of period of descent. Definitive aortic arch has curve of large radius. Short segment of right dorsal aorta distal to subclavian drawn out in slender thread End of period of rapid descent of heart and arteries; estimated average length 18 mm.; 50th day of development 1390 18 Definitive aortic arch sharply bent 460 20 Summit of definitive aortic arch at superior thoracic aperture 2937 24 Sternal bands in contact through most of their length 886 43 Origin of right and left pulmonaiy" branches in contact through most of their length    Age estimates based on Keibel F. and Mall FP. Manual of Human Embryology II. (1912) J. B. Lippincott Company, Philadelphia. curve of length and age.    Table as image   Table Reference: Congdon ED. Transformation of the aortic-arch system during the development of the human embryo. (1922) Contrib. Embryol., Carnegie Inst. Wash. Publ 277, 14:47-110.

Arch Cartilage

Meckel's cartilage, first pharyngeal arch

Pharyngeal arch cartilages

• Arch 1 - Meckel's cartilage, horseshoe shaped
  • dorsal ends form malleus and incus
  • midpart forms ligaments (ant. malleus, sphenomandibular)
  • ventral part forms mandible template

• Arch 2 - Reichert's cartilage
  • dorsal ends form stapes and Temporal bone styloid process
  • ventral part ossifies to form hyoid bone components
  • lesser cornu and superior body

• Arch 3- forms greater cornu and inferior part of hyoid

• Arch 4&6- form laryngeal cartilages, except epiglottis (from hypobranchial eminence)

Arch Muscle

• Arch 1 - muscles of mastication, mylohyoid, tensor tympanic, ant. belly digastric
• Arch 2 - muscles of facial expression, stapedius, stylohyoid, post. belly digastric
• Arch 3 - stylopharyngeus
• Arch 4&6 - crycothyroid, pharynx constrictors, larynx muscles, oesophagus (st. muscle)

Head and Heart Muscle On the left side of the body (right part of figure) the facial expression muscles have been removed to show the masticatory muscles.

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  Masseter

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  Stylopharyngeus

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  Pharynx constrictors

Arch Nerve

trigeminal

• Arch 1 - CN V trigeminal, caudal 2/3 maxillary and mandibular, cranial 1/3 sensory nerve of head and neck, mastication motor
• Arch 2 - CN VII facial
• Arch 3 - CN IX glossopharyngeal
• Arch 4&6 - CN X vagus, arch 4- superior laryngeal, arch 6- recurrent laryngeal

Arch Pouches

• Arch 1 - elongates to form tubotympanic recess, tympanic cavity, mastoid antrum, eustachian tube
• Arch 2 - forms tonsillar sinus, mostly oblierated by palatine tonsil
• Arch 3 - forms inferior parathyroid and thymus
• Arch 4 - forms superior parathyroid, parafollicular cells of Thyroid

Thyroid Gland

• not a pouch structure
• first endocrine organ to develop day 24
• from floor of pharynx
• descends thyroglossal duct (which closes)
• upper end at foramen cecum

Anterior Pituitary

Pituitary

• not a pouch structure
• boundary epitheilal ectoderm in the roof of the pharynx
• forms a pocket (Rathke's pouch) that comes into contact with the ectoderm of developing brain.
  • Rathke's pouch is named after German embryologist and anatomist Martin Heinrich Rathke (1793 — 1860).

Face Development

Begins week 4 centered around stomodeum, external depression at oral membrane

5 initial primordia from neural crest mesenchyme

• single frontonasal prominence (FNP) - forms forehead, nose dorsum and apex
• nasal placodes develop later bilateral, pushed medially
• paired maxillary prominences - form upper cheek and upper lip
• paired mandibular prominences - lower cheek, chin and lower lip

Frontonasal Process

Frontonasal prominence (Week 7, 44 - 48 days, CRL 13 - 17 mm)

The frontonasal process (FNP) forms the majority of the superior part of the early face primordia. It later fuses with the maxillary component of the first pharyngeal arch to form the upper jaw. Failure of this fusion event during the embryonic period leads to cleft lip. Under the surface ectoderm the process mesenchyme consists of two cell populations; neural crest cells, forming the connective tissues; and the mesoderm forming the endothelium of the vascular network.

A chicken developmental model study has identified a specific surface region, the Frontonasal Ectodermal Zone (FEZ), initially induced by bone morphogenetic proteins that appears to regulate the future growth and patterning of the frontonasal process. The specific frontonasal ectodermal zone was located in the frontonasal process ectoderm flanking a boundary between Sonic hedgehog (Shh) and Fibroblast growth factor 8 (Fgf8) expression domains.

Head/Skull

chondrocranium forms base of skull in lower vertebrates encases brain cranial vault calveria facial skeleton pharyngeal arches

Adult Skull MRI Links: Skull Development - MRI  ‎‎Viscerocranium Page | Play  ‎‎Temporal Bones Page | Play  ‎‎Occipital - Frontal Page | Play  ‎‎Parietal-Zygomatic Page | Play

Sensory Placodes

Sensory placodes (week 5)

• During week 4 a series of thickened surface ectodermal patches form in pairs rostro-caudally in the head region.
• Recent research suggests that all sensory placodes may arise from common panplacodal primordium origin around the neural plate, and then differentiate to eventually have different developmental fates.
• These sensory placodes will later contribute key components of each of our special senses (vision, hearing and smell). Other species have a number of additional placodes which form other sensory structures (fish, lateral line receptor). Note that their initial postion on the developing head is significantly different to their final position in the future sensory system

Otic placode

in the stage 13/14 embryo (shown below) the otic placode has sunk from the surface ectoderm to form a hollow epithelial ball, the otocyst, which now lies beneath the surface surrounded by mesenchyme (mesoderm). The epithelia of this ball varies in thickness and has begun to distort, it will eventually form the inner ear membranous labyrinth.

Lens placode

lies on the surface, adjacent to the outpocketing of the nervous system (which will for the retina) and will form the lens.

Links: Lens Development

Nasal placode

has 2 components (medial and lateral) and will form the nose olfactory epithelium.

Links: Smell Development | Placodes

Head Growth

Developing skull Computed Tomography (CT) image showing normal sutures.

• continues postnatally - fontanelle allow head distortion on birth and early growth
• bone plates remain unfused to allow growth, puberty growth of face

Fetal head growth (circumference)

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  Second and third trimesters

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  Second trimester

Skull Overview

Chondrocranium - formed from paraxial mesoderm

• cranial end of vertebral column
• modified vertebral elements
• occipital and cervical sclerotome
• bone preformed in cartilage (endochondrial ossification)

Cranial Vault and Facial Skeleton - formed from neural crest

• muscle is paraxial mesoderm
• somitomeres and occipital somites

Calveria - bone has no cartilage (direct ossification of mesenchyme)

• bones do not fuse, fibrous sutures 1. allow distortion to pass through birth canal 2. allow growth of the brain
• 6 fontanelles, posterior closes at 3 months, anterior closes at 18 months

Links: Skull Development

Palate

The palate has two key stages of development during embryonic and an early fetal involving the fusion of structures (epithelia to mesenchymal).

Embryonic

Primary palate, fusion in the human embryo between stage 17 and 18, from an epithelial seam to the mesenchymal bridge.

Fetal

Secondary palate, fusion in the human embryo in week 9. This requires the early palatal shelves growth, elevation and fusion during the early embryonic period. The fusion event is to both each other and the primary palate. palatal shelf elevation | secondary palate

Links: palate

Ear Auricles

• form from 6 hillocks (week 5)
• 3 on each of arch 1 and 2

Tongue Development

] ]

• Ectoderm of the first arch surrounding the stomodeum forms the epithelium lining the buccal cavity.
• Also the salivary glands, enamel of the teeth, epithelium of the body of the tongue.
  • As the tongue develops "inside" the floor of the oral cavity, it is not readily visible in the external views of the embryonic (Carnegie) stages of development.

• Contributions from all arches, which changes with time
• begins as swelling rostral to foramen cecum, median tongue bud

• • Arch 1 - oral part of tongue (ant 3/2)
  • Arch 2 - initial contribution to surface is lost
  • Arch 3 - pharyngeal part of tongue (post 1/3)
  • Arch 4 - epiglottis and adjacent regions

Tongue muscle

tongue muscle

• Tongue muscles originate from the somites.
  • Tongue muscles develop before masticatory muscles and is completed by birth.
• Masticatory muscles originate from the somitomeres.
  • These muscles develop late and are not complete even at birth.

Salivary Glands

• epithelial buds in oral cavity (week 6 to 7) extend into mesenchyme
• parotid, submandibular, sublingual

Links: Salivary Gland Development | Tongue Development | Development Animation - Tongue

Pharyngeal Arch Tables

Pharyngeal Arch	Nerve	Artery	Neural Crest (Skeletal Structures)	Muscles	Ligaments
1 (maxillary/mandibular)	trigeminal (CN V)	maxillary artery (terminal branches)	mandible, maxilla, malleus, incus	muscles of mastication, mylohyoid, tensor tympanic, ant. belly digastric	ant lig of malleus, sphenomandibular ligament
2 (hyoid)	facial (CN VII)	stapedial (embryonic) corticotympanic (adult)	stapes, styloid process, lesser cornu of hyoid, upper part of body of hyoid bone	muscles of facial expression, stapedius, stylohyoid, post. belly digastric	stylohyoid ligament
3	glossopharyngeal (CN IX)	common carotid, internal carotid arteries	greater cornu of hyoid, lower part of body of hyoid bone	stylopharyngeus
4	vagus (CN X) superior laryngeal branch	part of aortic arch (left), part right subclavian artery (right)	thyroid, cricoid, arytenoid, corniculate and cuneform cartilages	crycothyroid, soft palate levator veli palatini (not tensor veli palatini)
6	vagus (CN X) recurrent laryngeal branch	part of left pulmonary artery (left), part of right pulmonary artery (right)	thyroid, cricoid, arytenoid, corniculate and cuneform cartilages	larynx intrinsic muscles (not cricothyroid muscle)

Structures derived from Pouches

Each pouch is lined with endoderm and generates specific structures.

Pouch	Overall Structure	Specific Structures
1	tubotympanic recess	tympanic membrane, tympanic cavity, mastoid antrum, auditory tube
2	intratonsillar cleft	crypts of palatine tonsil, lymphatic nodules of palatine tonsil
3	inferior parathyroid gland, thymus gland
4	superior parathyroid gland, ultimobranchial body
5	becomes part of 4th pouch

Structures derived from Grooves

Only the first groove differentiates into an adult structure and forms part of the external acoustic meatus.

Structures derived from Membranes

At the bottom of each groove lies the membrane which is formed from the contact region of ectodermal groove and endodermal pouch. Only the first membrane differentiates into an adult structure and forms the tympanic membrane.

Movies

There are a number of movies representing development of different features of the head and face.

‎‎Face Development Page | Play

‎‎Palate (oral view) Page | Play

‎‎Palate (front view) Page | Play

‎‎Tongue Page | Play

‎‎Mandible Growth Page | Play

Links: Head and Face Movies | Movies

References

Reviews

Gupta P, Tripathi T, Singh N, Bhutiani N, Rai P & Gopal R. (2020). A review of genetics of nasal development and morphological variation. J Family Med Prim Care , 9, 1825-1833. PMID: 32670926 DOI.

Nagarajan M, Sharbidre KG, Bhabad SH & Byrd SE. (2018). MR Imaging of the Fetal Face: Comprehensive Review. Radiographics , , 170142. PMID: 29652578 DOI.

Abramyan J & Richman JM. (2018). Craniofacial development: discoveries made in the chicken embryo. Int. J. Dev. Biol. , 62, 97-107. PMID: 29616744 DOI.

Adameyko I & Fried K. (2016). The Nervous System Orchestrates and Integrates Craniofacial Development: A Review. Front Physiol , 7, 49. PMID: 26924989 DOI.

Kuratani S & Schilling T. (2008). Head segmentation in vertebrates. Integr. Comp. Biol. , 48, 604-10. PMID: 20607135 DOI.

Grevellec A & Tucker AS. (2010). The pharyngeal pouches and clefts: Development, evolution, structure and derivatives. Semin. Cell Dev. Biol. , 21, 325-32. PMID: 20144910 DOI.

Articles

Choe CP & Crump JG. (2015). Dynamic epithelia of the developing vertebrate face. Curr. Opin. Genet. Dev. , 32, 66-72. PMID: 25748249 DOI.

Shone V & Graham A. (2014). Endodermal/ectodermal interfaces during pharyngeal segmentation in vertebrates. J. Anat. , 225, 479-91. PMID: 25201771 DOI.

Thi Thu HN, Haw Tien SF, Loh SL, Bok Yan JS & Korzh V. (2013). Tbx2a is required for specification of endodermal pouches during development of the pharyngeal arches. PLoS ONE , 8, e77171. PMID: 24130849 DOI.

Search PubMed

Search term: Head Development | Pharyngeal Arch Development | | Face Development

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Books

Hinrichsen K. The early development of morphology and patterns of the face in the human embryo. Berlin ; New York : Springer-Verlag, c1985

Additional Images

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  Adult axial skeleton

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  Adult skull (lateral simplified)

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  Fetal head lateral (12 weeks)

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  Fetal head medial (12 weeks)

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  Fetal head section (12 weeks)

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  adult mandible

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  adult hyoid

Historic

Historic Disclaimer - information about historic embryology pages

Pages where the terms "Historic" (textbooks, papers, people, recommendations) appear on this site, and sections within pages where this disclaimer appears, indicate that the content and scientific understanding are specific to the time of publication. This means that while some scientific descriptions are still accurate, the terminology and interpretation of the developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these terms, interpretations and recommendations may not reflect our current scientific understanding.     (More? Embryology History | Historic Embryology Papers)

Development or the Face

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  Fig. 1. Showing the formation of the face by the Nasal, Maxillary, and Mandibular processes in an embryo of the 4th week.

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  Fig. 2. Showing the parts of the face formed from the Nasal, Maxillary and Mandibular processes.

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  Fig. 3. Showing the structures formed in the Mesial Nasal Processes.

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  Fig. 4. Showing the trough-shaped Vomer of the newly born.

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  Fig. 5. Showing the suture on the face between the premaxilla and maxilla in the skull of a young orang.

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  Fig. 6. Showing the structures formed in the Lateral Nasal Processes.

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  Fig. 7. Coronal section of the skull of a 7th month human foetus to show the cartilages of the Lateral and Mesial Nasal Processes and the bones formed round them.

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  Fig. 8. Showing the ingrowth of the palatal plates of the two maxillary processes early in the 2nd month. (After Kollmann.) .

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  Fig. 9. Showing the Hard Palate at birth. The premaxillary part is formed from the Mesial Nasal Processes ; the remainder by the Palatal Plates of the Maxillary Processes.

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  Fig. 10, a, b, c. Showing what become of the skeletons of the Mandibular Arch (Meckel's Cartilage) and Maxillary Process (Palato-quadrate Cartilage).

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  Fig. 10 D. Illustrating Gadow's view of the origin of the Auditory Ossicles and Tympanic Plate.

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  Fig. 11. Showing the manner in which the development of the Maxillary Antrum affects the size of the palate and position of the molar teeth.

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  Fig. 12. Showing the Centres of Ossification and age changes in the Lower Jaw.

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  Fig. 13. The chief types of the Temporo-Maxillary Articulation. A. Carnivorous Type. B. Omnivorous Type. C. Herbivorous Type.

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  Fig. 14. Showing the Chief Changes after birth in the form of the TemporoMaxillary Articulation.

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  Fig. 15 A. Sagittal Section showing the Stomodaeum and position of the Oral Plate in the 3rd week.

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  Fig. 15 B. Showing the parts of the Buccal and Nasal Cavities formed from the Stomodaeum. The relative position of the Oral Plate is indicated.

Development of the Pharynx and Neck

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  Fig. 21a. Showing the Visceral Arches and Cleft-depressions in the Pharyngeal Wall of a 4th week human Embryo. Each Visceral Arch contains an Aortic Arch. (After His.)

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  Fig. 21b. Showing the position of the Heart, Visceral and Aortic Arches in a fish. (Diagrammatic — after Gegenbaur.)

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  Fig. 22. Showing the Primitive Pharynx of a 3rd week embryo in sagittal section, bounded by the Visceral Arches. (After His.) .

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  Fig. 23. Showing the Floor of the Pharynx of a 4th week human embryo. (After His.)

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  Fig. 24. Schematic Section of a Visceral Arch.

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  Fig. 25. Showing the position of the External Cleft Depressions in the Adult.

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  Fig. 26. Showing what become of the Cartilages of the Visceral Arches.

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  Fig. 27. Showing what become of the Nerves of the Visceral Arches, hyoid arch) is represented by the chorda tympani and great superficial petrosal.

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  Fig. 28. Showing what become of the Aortic Arches in the adult. Only the shaded parts persist.

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  Fig. 29. The condition of the Eight and Left Doral Aortae in a 6th week human foetus.

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  Fig. 30. Showing the Buccal and Pharyngeal parts of the Tongue.

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  Fig. 31. Showing the origin of the tongue in the floor of the primitive pharynx. (After His.)

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  Fig. 32. Showing the origin of the Submaxillary and Sublingual Glands from furrows between the gum and tongue during the flth week. (After His.) .

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  Fig. 33. Showing the position of the Visceral Clefts in the Adult.

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  Fig. 34. Showing the origin of the Tonsil, Thymus, and Thyroid from the Internal Cleft Recesses during the 4th week. (After His.).

Terms

Head Terms (expand to view)

acephaly - term meaning absence of head, see skull and head abnormalities. branchial arch - see pharyngeal arch. brachycephaly - term meaning premature fusion of coronal suture, see skull and head abnormalities. clefting - the way in which the upper jaw forms from fusion of the smaller upper prominence of the first pharyngeal arch leads to a common congenital defect in this region called "clefting", which may involve either the upper lip, the palate or both structures, see palate and head abnormalities. coronal suture - skull term for the fibrous connective tissue joint that connects the frontal bone with the parietal bones. cranial fossae - skull term for the base bones of the cranial vault that form a container and support for the brain. cranial vault - skull term for the space formed by bones of the skull that enclose the brain. cysts - refers to a cervical sinus abnormality, remants of the cervical sinus remains as a fluid-filled cyst lined by an epithelium, see pharyngeal arch and head abnormalities. dolichocephaly - see scaphocephaly. exencephaly - term meaning brain outside skull, see skull and head abnormalities. fistula - refers to a pharyngeal membrane abnormality, a tract extends from pharynx (tonsillar fossa) beween the carotid arteries (internal and external) to open on side of neck, see pharyngeal arch and head abnormalities. lambdoid suture (lambdoidal suture) skull term for the fibrous connective tissue joint that connects the parietal bones with the occipital bone, and is continuous with the occipitomastoid suture. macrocephaly - term meaning large head, see hydrocephalus, skull and head abnormalities. Meckel's cartilage - (pharyngeal arch 1 cartilage) The mandible forms by intramembranous ossification beside this transient cartilage. The middle ear malleus and incus are thought to form from the ends of this cartilage. metopic suture - skull term for the fibrous connective tissue joint that connects the two fontal bones. In the adult skull this suture is not always present. micrencephaly - term meaning small brain, see neural, skull and head abnormalities. otocephaly - term meaning absence of lower jaw, see skull and head abnormalities. oxycephaly - (turricephaly) term meaning premature fusion of coronal suture + others, see skull and head abnormalities. pharyngeal arch - (branchial arch) a structure that forms in the cranial region of the embryo having contributions from all germ layers. In humans, the arches appear in week 4 (GA week 6) in a rostra-caudal sequence and are numbered (1, 2, 3, 4, and 6). Each arch contributes a different part of the head and neck and the associated components. pharyngeal cleft - (groove) surface ectoderm that externally separates each pharyngeal arch. In humans, only first pair persist as the outer ear external auditory meatus. pharyngeal groove - see pharyngeal cleft. pharyngeal membrane - surface ectoderm and pharynx endoderm contact region lying between each pharyngeal arch. In humans, only the first membrane pair persist as the tympanic membrane. pharyngeal pouch - pharynx endoderm internal out-pocketing that separates each pharyngeal arch. plagiocephaly - term meaning premature unilateral fusion of coronal or lambdoid sutures, see skull and head abnormalities. Reichardt's cartilage - (pharyngeal arch 2 cartilage) The superior portion of the hyoid forms the ventral portion of this cartilage and the middle ear stapes is thought to form from the ends of this cartilage. sagittal suture - skull term for the fibrous connective tissue joint that connects the two parietal bones in the midline. scaphocephaly - (dolichocephaly) term meaning premature fusion of sagittal suture, see skull and head abnormalities. sinuses - refers to a pharyngeal groove (cleft) abnormality, when a portion of the pharyngeal groove persists and opens to the skin surface, located laterally on the neck, see pharyngeal arch and head abnormalities. squamosal suture - skull term for the fibrous connective tissue joint that connects the squamous portion of the temporal bone with the parietal bones. suture - skull term for a fibrous connective tissue joint. In humans, the main sutures are coronal, sagittal, lambdoid and squamosal sutures, with the metopic suture (frontal suture) occurring as an anatomical variant in the adult skull. trigonocephaly - term meaning premature fusion of metopic suture, see skull and head abnormalities. turricephaly - see oxycephaly. vestiges - refers to a cartilaginous or bony developmental remnants that lie under the skin on side of neck, see pharyngeal arch and head abnormalities.

Palate Development (expand to see terms)

cleft - An anatomical gap or space occuring in abnormal development in or between structures. Most commonly associated with cleft lip and cleft palate. Term is also used to describe the external groove that forms between each pharyngeal arch during their formation. cleft lip - An abnormality of face development leading to an opening in the upper lip. Clefting of the lip and or palate occurs with 300+ different abnormalities. Depending on many factors, this cleft may extend further into the oral cavity leading to a cleft palate. In most cases clefting of the lip and palate can be repaired by surgery. cleft palate - An abnormality of face development leading to an opening in the palate, the roof of the oral cavity between the mouth and the nose. Clefting of the lip and or palate occurs with 300+ different abnormalities. In most cases clefting of the lip and palate can be repaired by surgery. Palate formation in the embryo occurs at two distinct times and developmental processes called primary and secondary palate formation. This leads to different forms (classifications) and degrees of clefting. hard palate - anterior part of the palate that becomes ossified. The posterior palate part is the soft palate. epithelial mesenchymal transition - (EMT, epitheliomesenchymal transformation) conversion of an epithelium into a mesenchymal (connective tissue) cellular organization. Process required during lip and palate developmental fusion. epitheliomesenchymal transformation - (epithelial mesenchymal transition) conversion of an epithelium into a mesenchymal (connective tissue) cellular organization. incisive papilla - anterior midline palate near the incisors lying at the end of the palatine raphe. levator veli palatini - Muscle forming part of the soft palate, elevates the soft palate for swallowing. mastication - (chewing) Process of crushing and grinding food within the mouth. maxilla - (pl. maxillae) upper jaw bone forming from the maxillary process of the first pharyngeal arch. medial edge epithelial - (MEE) opposing palatal shelves adhere to each other to form this epithelial seam. musculus uvulae Small muscle forming part of the soft palate lying within the uvula, shortens and broadens the uvula. palatine raphe (median raphe) palate midline ridge (seam) of the mucosa, from the incisive papilla to the uvula. palatal rugae - (palatine rugae, rugae) Transverse series of ridges forming on the secondary hard palate that are sequentially added during development as the palate grows. Involved in the process of mastication. palatal vault - (palatine vault) Term describing the curved "arch" shape of the palate that mainly develops postnatally. palate - The roof of the mouth (oral cavity) a structure which separates the oral from the nasal cavity. Develops as two lateral palatal shelves which grow and fuse in the midline. Initally a primary palate forms with fusion of the maxillary processes with the nasal processes in early face formation. Later the secondary palate forms the anterior hard palate which will ossify and separate the oral and nasal cavities. The posterior part of the palate is called the soft palate (velum, muscular palate) and contains no bone. Abnormalities of palatal shelf fusion can lead to cleft palate. palatine bones - Two bones that with the maxillae form the hard palate. palatogenesis - The process of palate formation, divided into primary and secondary palate development. palatoglossus - (glossopalatinus, palatoglossal muscle) Small muscle forming part of the soft palate required for swallowing. palatopharyngeus - (palatopharyngeal or pharyngopalatinus) Small muscle forming part of the soft palate required for breathing. pharyngeal arch - (branchial arch, Greek, branchial = gill) These are a series of externally visible anterior tissue bands lying under the early brain that give rise to the structures of the head and neck. In humans, five arches form (1,2,3,4 and 6) but only four are externally visible on the embryo. Each arch has initially identical structures: an internal endodermal pouch, a mesenchymal (mesoderm and neural crest) core, a membrane (endoderm and ectoderm) and external cleft (ectoderm). Each arch mesenchymal core also contains similar components: blood vessel, nerve, muscular, cartilage. Each arch though initially formed from similar components will differentiate to form different head and neck structures. philtrum - (infranasal depression, Greek, philtron = "to love" or "to kiss") Anatomically the surface midline vertical groove in the upper lip. Embryonically formed by the fusion of the frontonasal prominence (FNP) with the two maxillary processes of the first pharyngeal arch. Cleft palate (primary palate) occurs if these three regions fail to fuse during development. Fetal alcohol syndrome is also indicated by flatness and extension of this upper lip region. soft palate - (velum, muscular palate) posterior part of the palate that becomes muscular. Forms 5 muscles: tensor veli palatini, palatoglossus, palatopharyngeus, levator veli palatini, musculus uvulae. The anterior palate part is the hard palate. T-box 22 - (TBX22) a transcription factor that cause X-linked cleft palate and ankyloglossia in humans. Tbx22 is induced by fibroblast growth factor 8 (FGF8) in the early face while bone morphogenic protein 4 (BMP4) represses and therefore restricts its expression. (More? OMIM - TBX22) tensor veli palatini - (tensor palati, tensor muscle of the velum palatinum) Small muscle forming part of the soft palate required for swallowing. Transforming Growth Factor-beta - (TGFβ) factors induces both epithelial mesenchymal transition and/or apoptosis during palatal medial edge seam disintegration. uvula - (Latin = a little grape) a pendulous posterior end of soft palate used to produce guttural consonants. First named in 1695. Van der Woude syndrome - common syndromic cause of clefting (2% of cleft lip and palates). Van der Woude syndrome 1 1q32.2 Van der Woude syndrome 2 1p36.11 velopharyngeal insufficiency - (VPI) associated with cleft palate repair, describes the velum and lateral and posterior pharyngeal walls failing to separate the oral cavity from the nasal cavity during speech.

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Cite this page: Hill, M.A. (2023, December 1) Embryology Head Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Head_Development

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