Paper - Development and variation of the nerves and the musculature of the inferior extremity and of the neighboring regions of the trunk in man

Embryology - 16 Apr 2024        Expand to Translate
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Bardeen CR. Development and variation of the nerves and the musculature of the inferior extremity and of the neighboring regions of the trunk in man. Am J Anat. 1906;6:259–390.

Development And Variation Of The Nerves And The Musculature Of The Inferior Extremity And Of The Neighboring Regions Of The Trunk In Man

By

Charles R. Bardeen,

Professor of Anatomy, University of Wisconsin, Madison.

With 10 Plates And 7 Text Figures.

In a previous article in this journal (Bardeen and Lewis, 01), an outline was given of the early development of the limbs, body-wall and back in the human embryo. Lewis subsequently, 01, gave a more detailed account of the development of the arm, and I have recently, 05, described at some length the development of the spine and of the skeleton of the leg. The purpose of the following paper is a more detailed account of the development of the nerves and musculature of the leg and of the neighboring regions of the trunk and a consideration of the relation of developmental conditions to variations found in the adult. The embryological studies have been based chiefly on embryos belonging to the collection of Professor Mall of the Johns Hopkins University, who kindly placed them at my disposal. The statistical studies of nerve variation are based upon charts drawn from specimens in the dissecting rooms of the Johns Hopkins University and at the University of Wisconsin.

A. Outline of the Development of the Muscles and Nerves of the Inferior Extremity

I. General Features

For a description of the development of the external form of the limbs and of the chief features which characterize the earlier stages in the internal difierentiation, reference may be made to the three papers mentioned above. The posterior limb-bud is first seen as a massing of the mesenchyme at the posterior extremity of the Wolffian ridge, usually opposite the 21st to the 26th spinal segments. This mesenchyme arises in part from the axial mesenchyme, in part possibly from the somatopleure. There is no good evidence that in the mammals the myotomes contribute directly to it. On the contrary the myotomes are sharply marked off by a limiting membrane from the mesenchyme of the limb-bud until this has become extensively developed. Afterwards this limiting membrane disappears, but there is little likelihood that cells derived from the myotomes then wander any considerable distance into the limb-bud. See Bardeen, 00. A capillary network connected with the umbilical artery and the cardinal vein is formed in the limb-bud at an early period. Somewhat later nerves extend into the limb. At the same time the mesenchyme begins to be differentiated into skeletal, muscular and dermal regions. During the development of the limb it shifts distally so that the distal margin of the limb-bud is brought opposite the 27th and 28th, and sometimes also the 29th, spinal segments. As this occurs, bundles of nerve fibres from these more distal spinal segments extend into the limb-bud to contribute to the posterior nerves of the limb. In the adult the most distal nerve to contribute to the nerves of the limb varies from the 26th to the 29th, but is most commonly the 28th. (Bardeen and Elting, or). The number of spinal nerves contributing to the chief nerves of the limb varies from six to nine, but is usually seven or eight (Op. cit.). These variations are in all probability associated with variation in position of the limb-bud to the spinal axis during embryonic development.

The development of the main nerve trunks of the limb may be called the primary stage of nerve development and the associated variation in origin of the nerves, primary variation. As opposed to this primary development and primary variation We may call the growth which distributes the nerves within the limb the secondary stage of development and the variation there found secondary variation. During the primary period the spinal nerves send fibre bundles by direct paths to certain cutaneous areas and muscular anlages. During the secondary period the cutaneous nerves extend over the surface of the limb from the areas to which they are first distributed and the muscle anlages become differentiated into specific muscles to each of which nerve branches are given.

II. Primary Period of Nerve Development

The general structural relations at the period when the nerves begin to extend into the limb-bud are shown in Plate I, Figs. 1 and 2. In Fig. 1 are shown the right limb and the distal half of the trunk from the 17th (9th thoracic) to the 29th (4th sacral) spinal segments in Embryo II (length 7 mm., age 26 days). The limb-bud lies opposite the 21st to the 26th spinal segments. The coelom extends to a point opposite the 26th segment, but in the region of the limb it does not extend so far dorsally as in the thoracic region. In the figure several of the myotomes of the left side, the axial mesenchyme, the aorta, the left cardinal vein, the intestines and the uro-genital organs are not shown. A portion of the right cardinal vein and a portion of the right umbilical artery are represented, reduced in size for the sake of clearness. The umbilical artery curves about the distal extremity of the coelom. From the umbilical artery a branch passes into the limb-bud. Veins pass from the limb-bud into the cardinal vein. The blood-vessels of the limb exist at this time in the form of an irregular plexus.

The second, third and fourth lumbar nerves may be seen sending spreading bundles of nerve fibres into the dense tissue of the limb, dorsal to the cardinal vein. They extend, however, for no considerable distance into the limb-bud. The myotomes end abruptly near the base of the limb-bud.

Plate II, Fig. 1, represents the tissue differentiation in a section through the posterior limb-buds of Embryo II. At the left the bud is shown cut through an area near the distal extremity of the coelom. At the right the cut is more dorsal and extends through the tips of the lumbar spinal nerves.

In Plate I, Fig. 2, are shown the right limb and the posterior half of the trunk from the 26th (8th thoracic) to the 30th (5th sacral) spinal segments in a slightly older embryo (CLXIII, length 9 mm.). Bundles of nerve fibres from the five lumbar and first two sacral nerves have become anastomosed into a plexus from which in turn four nerves have sprung. These represent the femoral, obturator, tibial and peroneal nerves. Within the limb the central mesenchyme, near the axis of the embryo, has become condensed. This condensed mesenchyme represents the femur and hip bone of the adult limb. In the drawing the outline of this sclerogenous tissue is made diagrammatically sharp. The femoral portion of the skeletal mass fades gradually into the undifferentiated mesenchyme of the distal portion of the limb. It is this skeletal mass which seems to divide the bundles of nerve fibres into the four main divisions which constitute the origin of the four chief nerves of the limb. The main artery and vein of the limb are represented at a reduced scale. The border vein at this period is well developed (see also Fig. 0, Plate III of the article by Bardeen and Lewis, 01).

The differentiation of the tissue of the limb-bud, first noticed in a condensation of tissue in the region corresponding to where the femur projects against the hip girdle, is quickly followed by further changes. Externally there becomes visible a differentiation of the limb into footplate, crus and thigh, while within the limb-bud the further development of the skeleton is marked by condensation of tissue, scleroblastema, to form the anlage of the skeleton of the foot, leg, thigh and hip girdle. About the scleroblastema is a myogenous zone, the mg/oblastema, composed of a slightly less dense tissue. In Embryo CIX, length 11 mm., this zone is best marked in the region of the hip (Plate II, Fig. It is not clearly defined in the foot region. Between the myoblastema and the ectoderm lies a zone of less condensed tissue, the dermoblastema.

The chief nerves of the limb extend into the myoblastema. This is not a homogeneous layer. On the contrary from the time of its forma- tion regions which represent the anlages of muscles or groups of muscles may be more or less clearly distinguished from regions which represent intermuscular spaces. In Plate III, Figs. 1 and 2, an attempt has been made to outline the muscle masses which represent the anlages of future muscle groups in Embryo CIX, length 11 mm. It is impossible to do this with exactness because the various regions are indefinitely bounded.

In this embryo the pelvic portion of the skeleton consists of a central region continuous with the head of the femur. From this central acetabular portion spring iliac, ischial and pubic processes. The femur is short and thick. The tibia and fibula are fairly definitely outlined, the foot-plate less definitely so.

The main nerve trunks have grown for a considerable distance into the limb. From them several of the chief muscular and cutaneous branches have sprung. The figures show these branches fairly well. In addition to the intrinsic nerves of the limb the anterior and posterior border nerves are also represented.

In Fig. 1 it may be seen that the myotomes in the region of the body wall have fused to form the anlage of the abdominal musculature. The lower margin of this extends distally about to the 21st spinal (1st lumbar) nerve. In Fig. E, Plate V of the article by Bardeen and Lewis, OI, it is represented slightly too short. From the ventro—posterior extremity of the abdominal musculature a somewhat indefinitely differentiated band of tissue may be followed to the pubic process of the pelvic girdle.

A slight communicating branch connects the twelfth thoracic with the first lumbar nerve. The main portion of this latter nerve extends forward on the internal surface of the distal margin of the anlage of the abdominal musculature and gives off a lateral, “iliae,” branch. Ventrally the nerve divides into branches which represent the hypogastric and inguinal nerves. The 1st lumbar nerve also gives off a branch which passes to the lumbar plexus.

The obturator nerve arises from the first four lumbar nerves, passes through the obturator notch of the hip girdle and divides into two main divisions. Each of these terminates in a differentiated mass of tissue, the more anterior of which represents the adductor longus and brevis and the gracilis muscles, the more posterior, the obturator portion of the adductor magnus and possibly also the obturator externus muscle.

The tibial nerve arises from the fourth and fifth lumbar and first three sacral nerves. From it branches pass to muscle masses representing the obturator internus, quadratus femoris, hamstring, and the superficial and the deep posterior crural musculature. Distal to the tibial nerve the posterior cutaneous nerve of the thigh and the pudendal and caudal nerves may be seen.

In Fig. E, Plate V of the article by Bardeen and Lewis, or, the urachus was represented much foreshortened in order to reveal the muscle masses of the leg. In. Fig. 1, Plate III, the urachus is outlined in its true position as seen directly from the side.

In Plate III, Fig. 2, the genital an.d lumbo-inguinal nerves are seen passing ventro-laterally from the junction of the 1st and 2d lumbar nerves. The femoral nerve is seen passing outwards over the region of the acetabulum. It is surrounded laterally by the iliopsoas muscle mass and terminates in the quadriceps femoris muscle mass. From it arise lateral and anterior cutaneous branches, a branch which passes to the sartorius muscle mass, and the saphenous nerve.

The peroneal nerve arises from the 4th and 5th lumbar and first two sacral nerves, gives off branches for the anlages of the superior gluteal, inferior gluteal, short head of the biceps and peroneal muscle masses and terminates in the anterior crural muscle mass.

An idea of the relations of the main nerves as they enter the limb in Embryo CIX may likewise be gained from Plate III, Fig. 3. The pelvis, the abdominal and dorsal musculature, the lining of the body cavity, the border nerves and the main nerve trunks of the limb are here represented as viewed from in front. The femur and the main nerve trunks are shown cut in a plane somewhat distal to the head of the femur. The division of the main nerve trunks into separate branches for individual muscles is schematic.

III. Muscle Differentiation

At the period under consideration several possibilities of muscle differentiation must be considered. 1st.—The tissue which represents the muscle masses just mentioned may extend into the limb-bud with the

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Cite this page: Hill, M.A. (2024, April 16) Embryology Paper - Development and variation of the nerves and the musculature of the inferior extremity and of the neighboring regions of the trunk in man. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Paper_-_Development_and_variation_of_the_nerves_and_the_musculature_of_the_inferior_extremity_and_of_the_neighboring_regions_of_the_trunk_in_man

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