THE URINARY ORGANS. 



THE KIDNEYS. 



Kidneys, two in number, are situated in the back part of the abdomen, and 

 _L are for the purpose of separating from the blood certain materials which, 

 when dissolved in a quantity of water, also separated from the blood by the kid- 

 constitute the urine. 



They are placed in the loins, one on each side of the vertebral column, behind 

 the peritoneum, and surrounded by a mass of fat and loose areolar tissue. Their 

 upper extremity is on a level with the upper border of the twelfth dorsal vertebra, 

 their lower extremity on a level with the third lumbar. The right kidney is 

 usually on a slightly lower level than the left, probably on account of the vicinity 

 of the liver. 



The kidneys rest on the lower part of the Diaphragm and the fascia covering 

 the Quadratus lumborum and the Psoas magnus muscles. The right is covered in 

 front by right lobe of liver, peritoneum intervening, the descending portion of the 

 duodenum, and the beginning of the transverse colon; the left has in front the fun- 

 dus of the stomach, the tail of the pancreas, and the descending colon (upper part). 



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

 and rather more than one inch in thickness. The left is somewhat longer, though 

 narrower, than the right. The weight of the kidney in the adult male varies from 

 4J ounces to 6 ounces, in the adult female from 4 ounces to 5J ounces. The com- 

 bined weight of the two kidneys in proportion to the body is about 1 in 240. 



The kidney has a characteristic form. It is flattened and presents at one part 

 of its circumference a hollow. It is larger at its upper than at its lower extremity. 

 It has two surfaces, two borders, and an upper and lower extremity. 



Its ant' rior surt\n-e is convex, looks forward and outward, and is covered by 

 peritoneum. The upper part of this surface on the right side is in contact with the 

 under surface of the right lobe of the liver, on which it produces a slight concave 

 impression, the '//?/>/v.yxA> renalis ; below this the descending portion of the duode- 

 num and the hepatic flexure of the colon are connected to this surface, the former 

 by areolar tissue and the latter by its mesocolon. On the left side the upper part 

 of the anterior surface of the kidney (covered by peritoneum of lesser sac) is in 

 contact with the under surface of the stomach, and below this with the left extrem- 

 ity of the pancreas, whilst the lower part has anteriorly the splenic flexure of the 

 colon, and internally the last portion of the duodenum. 



The posterior surface is flatter than the anterior, and is imbedded in areolar 

 tissue, which separates it from the Diaphragm and from the anterior lamella of the 

 lumbar fascia covering the Quadratus lumborum and Psoas magnus muscle. It is 

 also in relation with the last dorsal, ilio-inguinal. and ilio-hypogastric nerves. 



The external border is convex, and is directed outward and backward. On the 

 left side it is in contact, at its upper half or more, with the spleen, and below with 

 the descending colon. On the right side, upper two-thirds, liver ; below, ascending 

 colon. 



The internal border is concave, and is directed forward and a little downward. 

 It presents a deep longitudinal fissure bounded by prominent anterior and poste- 

 rior lip. This fissure is the hilum, and allows of the passage of the vessels, nerves, 

 and ureter. 



The superior extremity, directed slightly inward as well as upward, is thick 



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