CHROMAFFIN BODIES: SUPRARENAL GLAND 



369 



the aortic chromaffin bodies (of Zuckerkandl) . These occur on either side of the 

 inferior mesenteric artery, ventral to the aorta and mesial to the metanephros. 

 At birth they attain a length of 9 to 12 mm. and are composed of cords of chromaf- 

 fin cells intermingled with strands of connective tissue, the whole being sur- 

 rounded by a connective tissue capsule. After birth the chromafi&n bodies de- 

 generate, but do not disappear entirely. 



Glomus Caroiicum. — Associated with the intercarotid sympathetic plexus is a 

 highly vascular chromaffin body known as the carotid gland. Its anlage has been 

 first observed in 20 mm. embryos. 



The Suprarenal Gland is de- 



P 

 veloped from chromaffin tissue which v„ 1 



becomes its medulla, and from meso- 

 dermal tissue which gives rise to its 

 cortex. In an embryo of 6 mm. the 

 anlage of the cortex is present, ac- 

 cording to Soulie, and is derived from 

 ingrowing buds of the coelomic epi- 

 thelium. At 8 mm. the glands are 

 definite organs and at 9 mm. their 

 vascular structure is evident. The 

 cellular elements of the cortex are at 

 first larger than the chromaffin cells 

 which give rise to the medulla. The 

 anlages of the glands form projections 

 in the dorsal wall of the coelom be- 

 tween the mesonephros and mesen- 

 tery (Figs. 221, 232 and 233). 



The chromaffin cells of the med- 

 ulla are derived from the coehac plexus 

 of the sympathetic system. In embryos of 15 to 19 mm. (Fig. 368) masses of these 

 cells begin to migrate from the median side of the suprarenal anlage to a central 

 position, and later surround the central vein which is present in embryos of 23 

 mm. The primitive chromaffin cells are small and stain intensely. They con- 

 tinue their immigration until after birth. The differentiation of the cortex into 

 its three characteristic layers is not completed until between the second and third 

 years. The inner reticular zone is formed first, next the fasciculate zone, and last 



the glomerular zone. 

 24 



Wl 



• " W^^^/'VJ F .iS' Mil 



Fig. 367. — Section through a chromafl&n body 

 in a 44 mm. human fetus (after Kohn). X 450. 

 p, Mother chromaffin cells; sy, sympathetic cells; 

 b, blood vessel. 



