Suprarenal Gland

The suprarenal gland develops from two components: (a) a mesodermal portion, which forms the cortex, and (b) an ectodermal portion, which forms the medulla. During the fifth week of development, mesothelial cells between the root of the mesentery and the developing gonad begin to proliferate and penetrate the underlying mesenchyme (Fig. 19.42). Here they differentiate into large acidophilic organs, which form the fetal cortex, or primitive cortex, of the suprarenal gland (Fig. 19.44A). Shortly afterward a second wave of cells from the mesothelium penetrates the mesenchyme and surrounds the original acidophilic cell mass. These cells, smaller than those of the first wave, later form the definitive cortex of the gland (Fig. 19.44, A and B). After birth the fetal cortex regresses rapidly except for its outermost layer, which differentiates into the reticular zone. The adult structure of the cortex is not achieved until puberty.

While the fetal cortex is being formed, cells originating in the sympathetic system (neural crest cells) invade its medial aspect, where they are arranged in cords and clusters. These cells give rise to the medulla of the suprarenal gland. They stain yellow-brown with chrome salts and hence are called chromaffin

Postganglionic Nerve Fibers
Figure 19.43 Relation of the preganglionic and postganglionic nerve fibers of the sympathetic nervous system to the spinal nerves. Note the origin of preganglionic fibers in the visceroefferent column of the spinal cord.

cells (Fig. 19.44). During embryonic life, chromaffin cells are scattered widely throughout the embryo, but in the adult the only persisting group is in the medulla of the adrenal glands.

Was this article helpful?

0 0
Hair Loss Prevention

Hair Loss Prevention

The best start to preventing hair loss is understanding the basics of hair what it is, how it grows, what system malfunctions can cause it to stop growing. And this ebook will cover the bases for you. Note that the contents here are not presented from a medical practitioner, and that any and all dietary and medical planning should be made under the guidance of your own medical and health practitioners. This content only presents overviews of hair loss prevention research for educational purposes and does not replace medical advice from a professional physician.

Get My Free Ebook


Post a comment