LECTURE XIII 



URINARY ORGANS 



The urinary organs are the kidneys, ureters, bladder, and 

 urethra. 



Kidneys. — These two important organs are situated in the 

 sublumbar regions and are supported in place by large blood 

 vessels and connective tissue. They differ in shape, size, and 

 location, the right kidney being larger, farther forward, and 

 more nearly round than the left. Each is covered by a fibrous 



capsule from which 

 bundles of connect- 

 ive tissue branch to 

 penetrate the organ 

 and form a frame- 

 work. 



Internal struc- 

 ture. The kidneys 

 have a rich blood 

 supply from the 

 renal arteries, which 

 branch directly 

 from the posterior 

 aorta. One set of 

 capillaries supplies 

 the Malphigian 

 body, the other supplies the tubules. A kidney is essentially 

 a mass of minute tubes held together by connective tissue, and 

 supplied with a large quantity of blood. On cutting open a 

 kidney we may see two distinct portions separated by a wavy 

 line, and a cavity at the root. The two portions are the cortical 

 (outside) and the medullary (center). 



The cavity at the root, called the pelvis, is merely the funnel- 

 shaped origin of the ureter. 



Urine tubules make up a large part of the bulk of the kidney. 

 Each tubule begins in the cortical portion, in a little sac like 



68 



Fig. 31. — Lengthwise Section op the Horse's 

 Kidney. 



a, cortical portion ; 6, medullary portion ; d, d, 

 d, pelvis; g, ureter. 



