THE URINARY ORGANS. 269 



responding circulatory disturbance. Conversely, a 

 disturbed circulation or an enlarged heart is indica- 

 tive of a possible nephritis. 



Nerves. The nerve supply is derived from the 

 cerebrospinal system and the sympathetic. Many 

 of these supply the blood-vessels, which they always 

 accompany, but some arborize among the renal 

 tubules, particularly those of the renal cortex. 



THE URETERS. 



The ureters are two muscular tubes that conduct 

 the urine from the kidneys to the bladder. The 

 dilated commencement of each ureter is called the 

 pelvis and lies with its base in the renal fissure, and 

 extends through the hilum to the lower portion of 

 the kidney where the ureter proper begins. Lateral 

 expansions of this pelvis extend to and enclose the 

 papillae of the Malpighian pyramids, on the surface 

 of which the collecting tubules open. These ex- 

 pansions are called calyces. 



The ureters measure from fourteen to sixteen 

 inches in length, and one-fourth inch in diameter. 

 Each ureter lies behind the peritoneum and passes 

 downward and inward to the brim of the pelvis, and 

 then forward and inward to the base of the bladder. 

 The ureters are about two inches apart as they enter 

 the wall of the bladder, through which they pass 

 obliquely for three-fourths inch to open on the 

 inner surface in two narrow and slit-like openings. 

 The oblique passage through the bladder wall acts 

 as a valve to prevent a return flow of urine. 



Structure. The walls of the ureter consist of an 



