THE URETHRA. 169 



is contracted, consists of an epithelial layer, tunica propria, and 

 submucosa. 



The epithelium lining the bladder consists of a few layers of 

 stratified squamous or transitional epithelium (Fig. 12), con- 

 tinuous with and similar to that lining the ureters and renal 

 pelvis. The superficial layer of cells in the epithelium is a 

 stratum of thick, squamous, or lenticular cells, possessing 

 sometimes more than one nucleus each ; the lower surfaces of 

 these cells exhibit indentations into which the underlying cells 

 project. The cells beneath this outermost layer are oval or 

 pyriform and perpendicular to the surface ; the two or three 

 layers beneath these are spheroidal or irregular germinal epi- 

 thelial cells. 



The epithelium rests on a firm fibrous tunica propria ; be- 

 neath this is a layer of loose or areolar submucous tissue con- 

 tinuous with the fibrous tissue permeating the muscular coat. 

 A few small racemose mucous glands are said to be present in 

 the mucosa of the base of the bladder. 



Outside the submucosa is the thick muscular layer, composed 

 of fasciculi of involuntary muscle supported in fibrous tissue. 

 The arrangement of the muscular fasciculi is rather indefinite, 

 but in general three layers can perhaps be distinguished : an 

 inner longitudinal layer ; a middle circular layer, thickened 

 at the neck of the bladder to form the sphincter vesicse ; and 

 an outer longitudinal layer. 



Outside of the muscular coat is a fibrous layer, of areolar 

 tissue, which over a large portion of the fundus of the bladder 

 is covered by peritoneum. 



The Urethra. 



The female urethra is lined internally with epithelium, strati- 

 fied squamous, or sometimes, it is said, simple columnar. The 

 epithelium rests on a firm tunica propria, which, especially 

 toward the meatus, has papillae projecting into the epithelium. 

 Beneath the tunica propria is a loose submucosa, which con- 

 tains expanded venous sinuses forming an erectile tissue. 

 Small racemose mucous glands (urethral or Littre's glands) 

 also occur in the submucosa, most numerous at the meatus. 

 The mucosa, consisting of the above-mentioned layers, lies in 



