Chap. XVII.] 



ELIMINATION. 



203 



Position and General Description of the Urinary Organs. 



The kidneys. — The kidneys are two compound tubular secret- 

 ing glands placed at the back of the abdominal cavity, one on 

 each side of the lumbar vertebrae. They are bean-shaped, with 

 the concave side turned towards the spine, and the convex side 

 directed outwards. Each kidney is about four inches (102 mm.) 

 long, two (51 mm.) broad, and one (25.4 mm.) thick, and ex- 

 tends from the eleventh rib 

 to nearly the crest of the 

 ilium, the right being a lit- 

 tle lower than the left in 

 consequence of the large 

 space occupied by the 

 liver. They are covered 

 by a tough envelope of 

 fibrous tissue called the 

 capsule of the kidney, and 

 are usually embedded in 

 a considerable quantity of 

 fat. 



The ureters. — The ure- 

 ters are the excretory ducts 

 of the kidneys. They arise 

 in the middle of the con- 

 cave side, or hilus, of each 

 kidney, and proceed ob- 

 liquely downwards and in- 

 wards through the lumbar 

 region of the abdomen into 

 the pelvis, to open ob- 

 liquely by two constricted 

 orifices into the base of the 

 bladder. Each ureter is of the diameter of a goose quill, from 

 sixteen to eighteen inches (406 to 457 mm.) long, and consists 

 of muscular tissue lined by mucous membrane. The muscular 

 coat is arranged in two la3^ers, an outer circular and an inner 

 longitudinal. Outside the muscular coat is a layer of fibrous 

 connective tissue carrying the blood-vessels and nerves with 

 which the tube is supplied. 



Fig. 122. — The Renal Organs viewed 

 FROM Behind. R, right kidney; A, aorta; 

 A?', right reual artery ; Vc, inferior vena cava ; 

 Vr, right renal vein; U, right ureter; Vu, 

 bladder; fJa, urethra. 



