EXCRETION 



151 



wall, opposite the last thoracic and the first two lumbar vertebrae. 

 Each kidney is enclosed in a thin fibrous capsule, surrounded by 

 loose fibrous tissue normally containing considerable fat. A 

 ureter leaves each kidney from the concavity on the median side 

 and proceeds to the bladder, a large saclike vesicle lying in the 



Fig. 97. Fig. 98. 



Fig. 97. — Excretory organ of Man, diagrammatic, a, aorta; b, urinary blad- 

 der; k, kidney (left); p, postcava; ra, renal artery (left); rv, renal vein (left); u, 

 ureter (left), extends from the pelvis of kidney to the base of bladder; ua, urethra, 

 a canal to the outside. 



Fig. 98. — A. Diagram to show the relations between the blood vessels and 

 the nephridial tubules of the human kidney. A, artery; c, capsule (glomerulus) 

 1 to 4, parts of tubule; t, straight collecting tubule which leads to the pelvis of 

 the kidney; v, vein. The arrows indicate the direction of blood flow. B, section 

 of the thick portion of a loop of Henle to show its relation to the blood capillary 

 (b). (Modified from Stohr.) 



lower part of the abdominal cavity against the abdominal wall. 

 A single duct, the urethra, leads from the bladder to the outside. 

 A single renal artery brings blood to the kidney and a single renal 

 vein drains it. There is no renal portal circulation. In the 

 kidney the renal artery breaks up into smaller branches, some of 

 which end in ordinary capillaries while others form glomeruli in 



