170 THE URINARY ORGANS. 



longitudinal folds. Outside the submucous tissue is a well- 

 marked non-striated muscular coat, having an inner longitudi- 

 nal and outer circular layer, and intermingled with elastic 

 tissue. Outside the muscular coat is fibrous tissue, in which 

 the urethra is imbedded. 



The male urethra : The walls of the male urethra are com- 

 posed of epithelium resting on a tunica propria (forming a 

 mucous coat), submucous tissue, and muscular tissue, and con- 

 tain numerous mucous glands. 



The epithelium lining the male urethra is of the transitional 

 variety at the vesical end, then changes to stratified columnar ; 

 throughout the middle and longest portion (penile) it is sim- 

 ple columnar, and for a short distance back of the meatus is 

 of the stratified squamous type. 



The epithelial layer rests on a fibrous tunica propria which 

 toward the meatus sends papillae into the epithelium. 



These layers form the mucosa, which in the flaccid condition 

 of the canal lies in longitudinal folds. 



Outside the tunica propria is the submucous layer of areolar 

 and loose fibrous tissue. 



In the penile portion of the urethra the submucous tissue 

 merges into the cavernous or erectile tissue of the corpus 

 spongiosum, which is enveloped in a strong fibrous sheath. 



The submucosa along the entire course of the male urethra 

 contains small racemose mucous glands, the urethral glands or 

 glands of Littre, lined with columnar epithelium and opening 

 into the urethral canal ; in the penile portion these glands are 

 scattered throughout the erectile tissue. 



The muscular coat of the urethra lies outside or within the 

 submucous coat. In the prostatic and membranous portions 

 the muscular layer lies beneath the submucosa, and consists of 

 inner longitudinal and outer circular fasciculi of non-striated 

 muscle. 



Outside these muscular layers in the membranous urethra 

 is an additional muscle, the voluntary compressor urethrse. 



In the penile portion of the urethra the muscular layer is 

 imbedded in the submucous tissue. Near the bulb the inner 

 longitudinal and outer circular layers of smooth muscle are 

 still present ; but anteriorly the circular layer disappears and 

 the longitudinal fasciculi become thinned and scattered. 



