An Embryological Study of Human Suprarenal Glands and ZUCKERKANDL's Paraganglia

Abstract

The results of my study on the suprarenal glands of early stage human embryo based on their silver-impregnated specimens may be summarized as follows.In my 20mm embryo, the plexus solaris containing numerous ganglia was found fairly well developed between the cortical body of rather large size and the aorta abdominalis. The sympathicoblasts in these ganglia, however, are round cells far smaller than the cortical cells and packed very closely. Very fine nerve fibres have been discovered amoug the groups of such cells, but their relation to the smypathicoblasts could not be made out with any certainty, for no neurofibrils were formed in the cell bodies and consequently no nerve processes were in formation. Thus, these blastocytes are nothing but uniform and entirely undifferentiated primitive cells. Accordingly, no ganglion cells, mantle cells or SCHWANN's cells are yet born.Such ganglia of primitive sympathetic cells are formed also on the medial side of the cortical body, out of which the cells immigrate further into the deeper part of the cortical stock. The immigration in this stage of embryonic life is advanced so little that its beginning may be probably set at a time short before this stage.In my 40mm embryo, the plexus coeliacus and the plexus suprarenalis become better developed and the ZUCKERKANDL's paraganglia also comes into incipient formation. The sympathetic cells in the ganglia of the plexus, however, show as yet no trace of differentiation. Only the nerve fibres running among them come to show strong silver-afffinity.The immigration from the vicinity of the cortical body into its inner part of the sympathetic cells accompanying nerve fibres is now very perceptible, and some cell groups are detected in sporadic existence in the central part of the body, the small cells in the groups being easily distinguishable from the far larger cortical cells. Such cells of the immgrating hordes sometimes penetrate as far as into the center of the cortical body by this stage, but yet no differention of them into medullar cells or ganglion cells sets in.The abdominal paraganglia quite identical in nature with the medullar tissue are found in incipient formation within the plexus solaris and around the abdominal aorta. The cells in these paraganglia are rather light large cells and a considerable number of nerve fibres showing more or less frequent change in size are found in these paraganglia.In my 80mm fetus, the nerve elements in the suprarenal plexus and the adrenal medulla originting therein show a considerably advanced differentiation. In the suprarenal plexus, the ganglion cells begin to send out nerve processes and to show the mutipolarity specific to the sympathetic ganglion cells. The development of such processes, however, is as yet very poor. SCHWANN's cells appear sporadically alongside the nerve fibres, but no mantle cells are yet to be formed around the nerve cells.In this stage, the suprarenal gland undergoes very interesting changes as follows. The suprarenal medulla enlarges in the central part of the gland, extending over an area somewhat larger than that of the certex in cross-section. The sympathetic cells begin to show differentiation and their suddenly inflated bodies are found containing granules probably showing ohromaffinity, while the cortical cells are reduced into small cells, large cells being found no more. The medullar tiasue comes to contain numerous nerve fibres, of which the terminal mode assimilates that in human adults. Groups of spmpathetic cells as yet utterly undifferentiated may be found here and there in the medullar tissue. These groups later on become the ganglia found in the medullar tissue in all probaility.