URETHRA 347 



ally become elongated and it changes to the simple or few-layered col- 

 umnar epithelium of the cavernous portion. In the dilatation of the ure- 

 thra near its distal end, the fossa navicularis, the epithelium becomes 

 stratified with its outer cells squamous; the underlying papillae of the 

 tunica propria become prominent, and the whole is the beginning of the 

 gradual transition from mucous membrane to skin. 



Glands. Small groups of mucous cells are scattered along the urethra, 

 and in the cavernous part, especially on the upper wall, they form pockets 

 called urethral glands (of Littre). Often these pockets are on the sides 

 of epithelial pits so that the glands are branched. Non-glandular pits 



Mucous membrane of the urethra. 



Epithelium. Tunica propria. Urethral glands. Submucosa. 



Tunica 



albuginea. 



Arteries. Connective tissue Bundle of smooth Venous spaces, 

 trabeculae. muscle. 



FIG. 349. TRANSVERSE SECTION OF THE PARS CAVERNOSA URETHRE.S OF MAN. X 28. 



also occur, known as urethral lacuna, and the "paraurethral ducts" near 

 the external orifice are large lacunas of various sorts. 



Two glands of considerable importance empty by irregularly dilated 

 ducts, i^ in. long, into the beginning of the cavernous urethra. The 

 bodies of these bulbo-urethral glands (Cowper's glands) are found one on 

 either side of the membranous urethra, in close relation with striated 

 and smooth muscle fibers. The end pieces, which are partly alveolar and 

 partly tubular, anastomose. They consist of mucous cells, with inter- 

 cellular secretory capillaries, and produce a clear, glairy mucus, discharged 

 during sexual excitement. The ducts, surrounded by thin rings of smooth 



