OrJiJSKKAL PUNCTIOHS OF THE KXDNEr 



3tJ7 



k 



der. From the bladder a common duct called the urethra 

 extends downward to the external urinary opening. 



Each kidney receives 

 from the abdominal 

 aorta an artery called 

 the renal artery. This 

 artery breaks up in the 

 Iddney into fine capil- 

 laries which are eventu- 

 ally collected into a vein 

 called the renal vein. 

 The two renal veins, 

 one from each kidney, 

 ultimately return the 

 blood to the inferior 

 vena cava. The renal 

 arteries and veins enter 

 and emerge from the 

 kidneys at the same 

 point as the ureters. 



General functions of 

 the kidney. — The kid- 

 neys receive the waste- 

 laden blood of the body through the renal arteries. 

 Out of this blood they take the waste material (mainly 

 urea) and form of it a secretion called urine (urea dis- 

 solved in water). The waste-freed blood then returns to 

 circulation by way of the renal veins, while the urine is 

 poured from the kidneys into the bladder as fast as it is 

 formed. When a sufficient quantity has collected in this 

 bladder, the muscular walls contract and the liquid is ex- 

 pelled from the body by way of the urethra and urinary 



Fig. 168 — The kidneys and connectiona; ft, k, 

 kidneys; n?, renal vein; ra, renal artery; 

 u, u, ureters; b, bladder. 



