The Urinary Organs,. 



THE KIDNEYS. 



THE Kidneys are glandular organs, intended for the secretion of the urine. 

 They are situated at the back part of the abdominal cavity, behind the perito- 

 neum, one in each lumbar region, extending from the eleventh rib to near the 

 crest of the ilium; the right being lower than the left, in consequence of the 

 large size of the liver. They are usually surrounded by a considerable quan- 

 tity of fat, and are retained in their position by the vessels which pass to and 

 from them. 



Relations. The anterior surface of the kidney is convex, partially covered by 

 the peritoneum, and is in relation, on the right side, with the back part of the 

 right lobe of the liver, the descending portion of the duodenum, and the ascend- 

 ing colon; and on the left side with the great end of the stomach, the lower end 

 of the spleen, the tail of the pancreas, and the descending colon. 



The posterior surface is flattened, and rests upon the corresponding crus of the 

 Diaphragm, in front of the eleventh and twelfth ribs, on the anterior lamella 

 of the aponeurosis of the trans versalis, which separates the kidney from the 

 Quadratus Lumborum, and on the Psoas Magnus. 



The superior extremity, directed inwards, is thick and rounded, and embraced 

 by the suprarenal capsule. It corresponds, on the left side, to the upper border 

 and on the right side to the lower border of the eleventh rib. 



The inferior extremity, small and flattened, extends nearly as low as the crest 

 of the ilium. 



The external border is convex, and directed outwards towards the parietes 

 of the abdomen. 



The internal border is concave, and presents a deep notch, the hilum of the 

 kidney, more marked behind than in front. At the hilum, the vessels, excre- 

 tory duct and nerves, pass into or from the organ; the branches of the renal 

 vein lying in front, the artery and its branches next, the excretory duct or 

 ureter behind and below. On the vessels the nerves and lymphatics ramify, 

 and much cellular tissue and fat surround the whole. The hilum leads into a 

 hollow space, the sinus, which occupies the interior of the gland. 



Each kidney is about four inches in length, two inches in breadth, and about 

 one inch in thickness; the left being somewhat longer and thinner than the 

 right. The weight of the kidney in the adult male varies from 4J oz. to 6 oz.; 

 in the female, from 4 oz. to 5J oz. The left kidney is nearly always heavier 

 than the right, by about two drachms. Their weight in proportion to the body 

 is about 1 to 240. The renal substance is dense, firm to the touch, but very 

 fragile, and of a deep-red color. 



The kidney is invested by a fibrous capsule, formed of dense fibro-areolar 

 tissue. This capsule is thin, smooth, and easily removed from the surface of 

 the kidney, to which it is connected by fine fibrous processes and vessels; and 

 at the hilum is continued inwards, lining the sides of the sinus, and at the bot- 

 tom of that cavity forms sheaths around the bloodvessels, and the subdivisions 

 of the excretory duct. 



On making a vertical section through the organ, from its convex to its con- 

 cave border, it appears to consist of two different substances, viz., an external 

 or cortical, and an internal or medullary, substance. 



The -cortical substance forms about three-fourths of the gland. It occupies the 

 surface of the kidney, forming a layer about two lines in thickness, where it 



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