Paper - Observations in connection with the early development of the human suprarenal gland
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Wieman HL. Observations in connection with the early development of the human suprarenal gland. (1920) Anat. Rec.
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Observations in Connection with the Early Development of the Human Suprarenal Gland
H. L. Wieman
Zoological Laboratory, University of Cincinnati
Two Plates (Nine figures)
The purpose of this contribution is to call attention to certain details in connection with the development of the human suprarenal gland, because they happen to be clearly illustrated in the material at hand. This material consists of two human embryos, nos. 1 and 4 of the author’s collection, which were obtained some years ago, freshly killed and fixed, from Drs. H. L. VVoodward and Charles Goosmann, of Cincinnati. No. 1 had been killed in a bichromate-acetic mixture, and no. 4 in Bouin’s solution. The former measured 9 mm., crown—breech, and the latter 12 mm. Both measurements were made in 85 per cent alcohol after fixation, so that the sizes of the living embryos were somewhat larger than these figures. The embryos were embedded in paraffin, cut into serial sections of 10 [1, thickness, and stained on the slide with Delafield haematoxylin and orange G according to the method of Morris (’09). Mitotic figures abound in both embryos, but the fixation is somewhat better in no. 1.
Embryo no. 1, .9 mm. The suprarenal glands are not recognizable as distinct organs, but consist of a thickening in the mesenchyme on either side of the root of the mesentery, forming a pair of broad ridges projecting into the body cavity from the dorsal body wall. Anteriorly these suprarenal ridges are continuous with the dorsal portions of the pleuroperitoneal membranes, while posteriorly they blend with the genital ridges. Laterally each is separated from the mesonephros by a distinct groove (fig. 1). Occasionally a transverse section of a blood capillary can be seen in the center of each ridge, the beginning no doubt of the central vein of the adult organ.
The ridges are made up of mesenchyme which shows no evidence of differentiation. The ramus communicans divides into two at the level of the sympathetic ganglion where one of the branches terminates, the other passing ventralward into the mesenchyme. The cells composing the sympathetic ganglia stain more deeply than the surrounding cells, but beyond this they show no appreciable differentiation. The ganglia lie on either side of the aorta somewhat dorsal to it. The nerve strands (axis cylinders?) are easily distinguished and followed, owing to the fact that they stain readily with orange G. The ventral branch of the ramus communicans, which is really the direct ventral continuation of the latter, loses itself in the mesenchyme of the suprarenal region. It seems to be unaccompanied by nerve cells (fig. 3). From the picture one gets the impression that the nerve fibers are pushing their way through the mesenchyme, blazing, as it were, a track along which the ganglion cells are to follow later.
In the posterior part of the suprarenal ridge, the genital ridge, the subepithelial region of the mesonephros, and in the mesentery, one finds large cells with clear cytoplasm and standing out distinctly from all cells (fig. 3, 4, 5). These 1 take to be germ cells (primary genital cells). Their wide extraregional distribution indicates that these cells undergo a rather extensive migration before reaching the germinal epithelium. This of course is in keeping with what is known about the early development of germ cells in other vertebrates.
Embryo no. 4, 12 mm. The suprarenal glands in this specimen are distinctly marked off from the surrounding tissues (fig. 2). Each one lies with its dorsal surface against the pleuroperitoneal cushion, while in close contact with its median side are bundles of nerve fibers and -ganglionic clumps. Near the ventral border, as shown in figure 2, some nervous tissue is pushed into the substance of the gland, but only to a very slight extent, definite immigration, according to other authors, not taking place until a much later period.
The prevertebral sympathetic ganglion is now a very distinct mass of cells clearly difierentiated from the mesenchyme. Its relation to the ramus communicans is somewhat different from that described for the 9-mm. embryo. There is no longer any evidence of a branching in the ramus cominunicans at the level of the ganglion, the latter lying more directly in the path of the ramus. The ventral extension of the ramus (fig. 1) now passes directly ventralward from the ganglion (fig 2, 2).r.). Among the nerve fibers of the ventral extension of the ramus can be seen two kinds of cells: 1) those distinguished by a long narrow outline with nucleus of the same shape, which are probably sheath cells and, 2) large irregular cells with yellowish cytoplasm drawn out into processes and possessing rounded nuclei. The latter are undoubtedly migrating nerve cells (fig. 7). They are larger and difi'er otherwise in their appearance from the nerve cells found in the prevertebral ganglia (fig. 6), but are practically identical with the large nerve cells partially embedded in the ventral border of the suprarenal gland (figs. 2, 8). Comparing the pictures presented by figures 1 and 2 -it would seem that in the latter stage the nerve cells are in the actual process of migrating ventralward along the paths marked out by the nerve fibers, which alone are present in the former stage. If some of these migrating nerve cells are destined to enter the gland to form its chromaffin tissue and others to pass on to form the ganglia of the coeliac plexus, there is no way in the preparations at hand of distinguishing the two kinds. According to Souilé (’03), the penetration of the cortical portion of the suprarenal by the parasympathetic cells commences at the 19-mm. stage, which is of course considerably older than the one dealt with here.
The cells of the gland itself are arranged in the form of a branching network penetrated with blood-vessels, and resembling the zona reticularis of the adult organ. A distinct endothelium forms the walls of the capillaries (fig. 9). The only other indication of differentiation in the gland is the ingrowing of connective tissue trabeculae at the periphery.
His, Jun. (’91), described a preliminary nerve-fiber framework laid out in the form of rami communicantes, along which the sympathetic cells wander to form the ganglia. Streeter (Keibel and Mall, v. 2, p. 149) states that in human embryos the migrating cells can be recognized in advance of the loose strands of the tip of the growing nerve which extend through the mesenchyme toward the aorta, and that by the time a Well-defined nerve trunk is established, the sympathetic cells have already completed that part of their migration, and the cells then found on the nerve trunk are sheath cells only.
In the 9-mm. embryo under discussion the nerve fibers forming the ventral extension of the ramus communicans beyond the sympathetic ganglia (fig. 1) may have been preceded by amigration of ganglion cells through the mesenchyme, but my preparations do not show nerve cells either among the fibers or at their distal ends (fig. 3). On the other hand, in the 12-mm. embryo the cells found scattered along the course of the fibers are undoubtedly nerve cells rather than sheath cells. I am therefore inclined to believe that some at least of the ganglia migrate to their final location along paths formed of nerve fibers. The well-known work of Harrison (’06) which shows very conclusively that ganglion cells of amphibian larvae develop axis cylinders as outgrowths of the cell body, strengthens my conviction that the nerve fibers forming the pathway develop originally as outgrowths from cells located in the cord. Whether the nerve cells subsequently found among the nerve fibers come directly from the spinal ganglia or from the prevertebral ganglia is another question. I can only say that the migrating nerve cells are larger and differ in outline from those found in the prevertebral ganglia.
As has been noted above, Soulié (’03) states that the penetration of the parasympathetic cells into the cortical portion of the suprarenal gland commences at the 19-mm. stage. Zuckerkandl (Keibeland Mall, v. 2, p. 173) states that the elements of the migrating cell masses, which are entirely or for the most part chromaffin-forming cells, are sharply distinguished from the neighboring cortical cells by their smallness and intense stain. In my preparations one cannot say with certainty Whether such cells are present or not. Deeply staining cells occur bordering the nerve strands and the ganglionic masses, and these may represent the chromaﬂin cells, but if so they are sharply defined from the nerve cells and are more distinctly epithelial in character.
Zuckerkandl (Keibel and Mall, V. 2, p. 171) found that the suprarenal glands are already vascularized in a 9-mm. embryo, whereas in my specimen of this age the only indication of vascularization is the occasional appearance in the suprarenal ridges of a cross-section of a blood capillary, which simply means that my embryo is younger than his, though both are the same length. In the 12-mm. embryo of my collection delicate endothelial capillaries form a very rich vascular network involving practically all of the gland except the cortical region. The central vein is not visible.
Hoffmann (93) and others have shown that the primordial germ cells are distinct from the elements making up the germinal epithelium of the gonad and that they exist a long time before the appearance of the latter. More recently, Swift (’14) has traced the history of the primordial germ cells of the chick from their origin in a specialized region of the germ-wall entoderm just at the margin of the area pellucida. These cells are carried by their own movement and later by that of the blood to all parts of the embryo and Vascular area until in embryos of twentysix to twenty-nine somites they are found in the splanchnic mesoderm near the radix mesenterii. With the formation of the gonad they gradually pass to that organ. Fuss (’11) describes extraregional germ cells in a human embryo aged four Weeks. He finds them in the mesentery directly under the peritoneum, but not in the germinal epithelium. According to his description, they are large cells of rounded outline, with clear cytoplasm and distinct nucleus. The cells measure 19 to 20 p in diameter and the nuclei 12.75 p.
In my 9-mm. embryo, which is somewhat older than the one studied by Fuss, I have found cells resembling the one pictured by Fuss in his figure and corresponding in every way to those described in his text, except that the measurements I have made are somewhat less than his. Likewise I find the distribution of these primitive germ cells to be somewhat wider than he found, and in my preparations some of the cells have approached very close to the germinal epithelium (fig. 4). The 12—mm. embryo did not prove favorable for the study of these cells, so that I have no data on the range of distribution at this later stage. My observations on the 9-mm. embryo corroborate the statements of Fuss, which indicates that the germ cells of man like those of other vertebrates are characterized by period of migration in the early part of their history.
- The suprarenal ridges extend from the pleuroperitoneal membranes posteriorly to the genital ridges.
- The only indication of vascularization in the suprarenal tissue consists in an occasional cross-section of a capillary.
- In the suprarenal region the rami communicantes extend ventrally beyond the prevertebral sympathetic ganglia as nerve fibers apparently free of nerve cells.
- Extraregional germ cells are found widely scattered in the neighborhood of the genital ridges.
- The suprarenal glands are distinctly marked off from surrounding tissues.
- The central region of the gland is in the form of a network, and is highly vascular, the blood-vessels having distinct endothelial walls.
- The median side of each gland is in close contact with the ventral prolongation of the ramus communicans and masses of ganglia cells. Some of the latter are found among the fibers of the distal part of the ramus along which they seem to be migrating to form the coeliac and visceral plexuses.
FUSS, A. 1911 Ueber extraregionare Geschlechtszellen bei einen menschlichen Embryo Von vier Wochen. Anat. Anz., Bd. 39.
HARRISON, R. G. 1906 Further experiments on the development of peripheral nerves. Am. Jour. Anat., vol. 5.
HIS, W., JUN. 1891 Die Entwicklung des Herznervensystems bei Wirbeltiere. Abh. d. math.-phys. Kl. d. Kgl. Sachs. Ges. (l. Wiss., Bd. 18.
HOFFMANN, C. K. 1893 Etude sur le développement de l’appareil urogenital des oiseaux. Verh. d. Kgl. Akad. V. Wetenschoppen. Amsterdam, vol. 1.
MORRIS, J. T. 1909 A note on orange—G counterstaining suggesting a. useful method in the management of embryonic tissue. Anat. Rec., vol. 3.
SOULIE, A. H. 1903 Recherches sur le développement des capsules surrénales. Journ. de l’Anat. et de la Physiol., vol. 39.
SVVIFT, C. H. 1914 Origin and early history of the primordial germ cells in the chick. Am. Jour. Anat., vol. 15.
Description of Figures
figs. 1 and 2 are camera drawings made at table level with Zeiss ocular 2- and 16-mm. objective. The remaining figures were made with Zeiss ocular 4- and 2—mm. objective. All figures have been somewhat reduced in reproduction.
Abbreviations used in Figures
b.v., blood-vessel p.c., pleuroperitoneal cushion
e.c., endothelial cell s.g., prevertebral sympathetic gang.c., primordial germ cell glion
g.r., germinal ridge s.r., suprarenal ridge
n.c., nerve cell v.r., ventral continuation of the ramus n. f ., nerve fiber communicans
EXPLANATION OF fiGURES
1 Transverse section through suprarenal region of 9-mm. embryo.
2 Transverse section through suprarenal region of 12—rnm. embryo.
3 Enlargement of portion of ventral continuation of the ramus communicans of figure 1.
4 Enlargement of portion of germinal ridge of figure 1, showing a primordial germ cell near the germinal epithelium.
5 Enlargement of portion of subepithelial portion of the suprarenal ridge of figure 1 also showing a primordial germ cell.
6 Enlargement of portion of the prevertebral ganglion of figure 2.
7 Enlargement of the ventral continuation of the ramus communicans of figure 2.
8 Enlargement of the ganglionic mass embedded in the ventral border of the suprarenal gland of figure 2.
9 Enlargement of the central portion of the suprarenal gland of figure ‘2, showing the capillary structure.
Cite this page: Hill, M.A. (2019, July 21) Embryology Paper - Observations in connection with the early development of the human suprarenal gland. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Paper_-_Observations_in_connection_with_the_early_development_of_the_human_suprarenal_gland
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