882 THE DEVELOPING ENDOCRINE GLANDS 



7. Adrenal (Suprarenal) Glands 



The adrenal bodies are associated, as the name impUes, with the renal 

 organs or kidneys. In fishes, definite adrenal bodies are not present, but 

 cellular aggregates, corresponding to the adrenal cells of higher vertebrates, 

 are present and associated with the major blood vessels. 



In man and other mammals, the adrenal body is composed of: 



( 1 ) an outer, yellow-colored cortex and 



(2) an inner medullary area. 



The medulla contains the chroniaffin cells — cells which have a pronounced 

 aflfinity for chromium salts, such as potassium dichromate, which stain them 

 reddish brown and produce the so-called "chroniaffin reaction." 



The hormone, secreted by the medulla, is adrenaline (epinephrine). It has 

 marked metabolic and vasoconstrictor effects. The smooth muscle tissue of 

 the arrecfor pili muscles associated with the hairs in mammals contract and 

 raise the hair as a result of adrenaline stimulation. 



The morbid state, known as Addison's disease and named after the English 

 physician, Thomas Addison, who first described this fatal illness, arises from 

 decreased function of the adrenal cortex. Various types of hormones have 

 been discovered which arise from the cortical layer of the adrenal body, and 

 a large number of steroid substances have been isolated from this area of the 

 adrenal gland (Selye, '48, p. 89). In fishes, the cortical cell groups are isolated 

 from those of the medulla, and, in the elasmobranch fishes, the cortex forms 

 a separate organ. Its removal may be eflfected without injury to the medulla 

 but with resulting debility, ending in death. 



Embryologically, the adrenal cortex and medulla take their origin from 

 two distinct sources. The cortex arises as a proliferation of the dorsal root of 

 the dorsal mesentery in the area near the anterior portion of the mesonephric 

 kidney and liver on either side (fig. 3 67 A, B). These two proliferations give 

 origin to two cortical masses, each lying along the anterior mesial edge of 

 the mesonephric kidney. Further growth of these masses produces two rounded 

 bodies, the adrenals (suprarenals), lying between the anterior portions of 

 the mesonephric kidneys (figs. 3A and B; 367B) and later in relation to the 

 antero-mesial portion of the metanephric kidneys (fig. 3B-E). After the cor- 

 tical masses are established, the chroniaffin cells invade them from the medial 

 side (fig. 367C), The potential chromaffin cells migrate from the sympathetic 

 ganglia in this area. Upon reaching the site of the developing adrenal gland 

 they move inward between the cortical cells to the center of the gland where 

 they give origin to the medulla. With the diverse embryological origins of 

 the cortex and the medulla, it is seen readily why two separate glandular 

 structures are present in lower vertebrates. 



In man and other mammals, a later developed secondary cortex is laid 

 down around the primary cortex. The primary cortex, characteristic of fetal 



