THE URINARY ORGANS. 



337 



The mucosa often contains diffuse lymphoid tissue, which is more 

 highly developed in the region of the renal pelvis. Here also 

 there are found folds or ridges of mucosa which extend into the 

 epithelium and present the appearance of papillae when seen in 

 cross-section. A few mucous glands are also met with in the 

 pelvis and in the upper portion of the ureter in certain mammals; 

 in man, however, no typical glands are found, although solid 



Superficial epi- 

 thelial cells. 



Mucosa. 



Epithelium. 



Mucosa. 



Inner longitud- 

 inal muscular 

 layer. 



Middle circular 

 muscular 

 layer. 



Outer muscular 

 layer. 



Fig. 271. Section of lower part of human ureter ; X I 4- 



epithelial buds, which extend into the mucosa for a distance, have 

 been described. The ureter possesses two layers of nonstriated 

 muscle-fibers the inner longitudinal, the outer circular. From the 

 middle of the ureter downward a third external muscular layer is 

 found with nearly longitudinal fibers. 



The urinary bladder has no glands, and its musculature appar- 

 ently consists of a feltwork of nonstriated muscle bundles^ a condi- 



22 



