THE ADRENAL BODIES 



563 



THE ADRENAL BODIES 



The adrenal bodies or glands (Glanduls adrenales)i are two small, flattened 

 organs, which lie m contact with the anterior part of the medial border of the 

 kidneys (Figs. 496, 497). They are ductless. In the horse they are red-brown in 

 color, about three and a half to four inches (ca. 9 to 10 cm.) long, one to one and a 

 half inches (ca. 3 to 4 cm.) wide, and about half an inch or more (ca. 1.5 cm.) in 

 thickness. ^ The weight varies from one to two ounces (ca. 28 to 56 gm.). 



The right adrenal body is related medially to the posterior vena cava, to which 

 it is adherent. Its anterior part curves dorsally around the medial border of the 

 right kidney. Its posterior part is flattened and is related ventrally to the pancreas 

 and ctecum, dorsally to the right renal vessels. The anterior extremity is con- 

 cealed in the renal impression of the liver; the posterior is related to the ureter. 



The left adrenal body is a little shorter than the right one, and its extremities 

 are rounded; it is usually curved, so that its medial border partly embraces the 

 anterior mesenteric artery. Its dorsal surface is related 

 to the Iddney, the renal artery, the aorta, and the left 

 coeliaco-mesenteric ganglion. The ventral surface is in 

 relation with the left extremity of the pancreas and the 

 root of the great mesentery. The posterior extremity 



often curves inward behind the anterior mesenteric ^ W-fl! ^ z 



artery; it is related behind to the left renal vein. 



When hardened in situ the adrenals present several features 

 not evident in the soft organs. The anterior part of the right 

 adrenal is twisted dorso-laterally over the medial margin of the 

 kidney, so that this part is prismatic and has three surfaces; of 

 these, the concave lateral one is applied to the kidney, the dorsal 

 one is related to the right crus of the diaphragm and the liver, 

 and the rnedial one is in contact with the posterior vena cava. 

 The anterior mesenteric artery is nearly always more or less en- 

 larged as a result of verminous arteritis, and the form and degree 

 of curvature of the left adrenal seem to vary in conformity with 

 the condition of the artery. 



Structure. — The fibrous capsule adheres intimately 

 to the surface of the organ. It contains elastic fibers, 

 and in its deep part unstriped muscle-fibers. From it 

 trabecule pass radially into the substance, blending 

 with the fine supporting reticulum. The parenchyma 

 consists of a cortical and a medullary part. The cor- 

 tical substance (Substantia corticalis) is red-brown in 



color, and is clearly distinguishable from the yellow medullary substance (Substantia 

 medullaris) . A large central vein (Vena centralis) is visible on cross-sections. 



The cells of the cortex are arranged in chains of one or two ro'ws. In the peripheral portion 

 the ceUs are of high cylindrical shape, and the chains form connecting loops; Giinther has pro- 

 posed the name zona arcuata for this part, instead of the usual tcim zona glomerularis. More 

 deeply the chains are distinctly palisade-like, and this region is called the zona fasciculata. Next 

 to the medulla is the zona reticularis, in which the chains form a network. The cells in these two 

 zones are polygonal and contain a brown pigment. The cells of the medulla are arranged in 

 irregular groups or form sheaths around the veins. They react to chromic salts by assuming a 

 yellow or yellow-brown color, and are termed chromaffin cells; they share this peculiarity with 

 certain cells of the sympathetic ganglia and paraganglia, with which they are probably related 

 genetically. The alkaloid adrenalin appears to be formed in the medullary cells. 



Vessels and Nerves. — The adrenals receive a relatively large blood-supply 

 through the adrenal arteries, which arise from the renal arteries or from the aorta 

 directly. The veins terminate in the posterior vena cava and the left renal vein. 



^From the standpoint of comparative anatomy the term "adrenal" is decidedly preferable 

 to "suprarenal." 



Fig. 51)3. — Adhenal Body op 

 Horse; Horizontal .Sec- 

 tion, Reduced. 

 1, Capsule; 2, 2', cortical 



substance; 3, medullar;' substance; 



A, blood-vessel in section. (From 



Leisering's Atlas, reduced.) 



