452 



THE URINARY SYSTEM 



the organ its outer fibrous coat is covered by the peritoneum, the con- 

 nective tissue of which is indistinguishable from that of the outer coat 

 of the bladder ; it is clothed by the peritoneal mesothelium. 



Vascular and Nerve Supply. The vascular and nerve supply of 

 the bladder is exactly similar to that of the ureter. The larger blood- 



FIG. 416. EPITHELIAL CELLS FROM THE BLADDER OF THE RABBIT. 



A, as seen from the under surface, showing the depressions made by the under- 

 lying polygonal and pyriform cells (P); B, side view of similar cell. (After Klein, 

 from Schafer.) 



vessels occur in the outer fibrous coat, whence they distribute branches 

 to the muscular coat and mucous membrane. Many small ganglia are 

 also found in the outer coat, and motor and sensory nerves are dis- 

 tributed to the musculature and to the epithelium and connective tissue 

 of the mucosa, as in the ureter. 



THE URETHRA 



THE FEMALE URETHRA 



The mucosa of the female urethra is lined by a variable type of 

 epithelium. Being continuous with the mucosa of the bladder, the 

 epithelium of the urethra is at first of the transitional variety, but as 

 it approaches the meatus this is changed to a stratified squamous 

 type which is continuous with that of the vestibule. In certain indi- 

 viduals the superficial cells of the midportion of the urethra are much 

 elongated and assume an irregular stratified columnar type. 



The epithelium rests upon a tunica propria of dense areolar con- 

 nective tissue whose outer portion blends with a looser connective 



