326 



HISTOLOGY 



is exclusively the outlet of the urinary tract. The epithelium has been 

 variously described as stratified, with outer squamous cells, or as pseudo- 

 stratified, and columnar. It may be of different forms in different indi- 

 viduals. The lumen is irregularly crescentic, with longitudinal folds 

 (Fig. 325). Branched tubular urethral glands are found only in small 

 numbers, except near the outlet. Their secretion is mucoid, but is not 

 typical mucus. In the submucosa there are many thin-walled veins con- 



FIG. 325. CROSS SECTION OF THE FEMALE URETHRA. (Koelliker.) 



d., Gland-like diverticulum; e., epithelium; L., lumen of the urethra; m., striated muscle; s., corpus spongi- 

 osum. containing venous spaces (v) and smooth muscle. 



stituting the corpus spongiosum. This is comparable with the upper 

 part of the more highly developed corpus cavernosum urethras of the male. 

 (Compare with Fig. 349, p. 347.) The muscularis is a thick layer, consist- 

 ing of inner longitudinal and outer circular smooth muscle fibers, among 

 which the veins extend, and connective tissue with many elastic fibers is 

 abundant. The striated constrictor urethra is outside of the smooth muscle 

 layer, as shown in the figure. 



MALE GENITAL ORGANS. 



DEVELOPMENT AND GENERAL FEATURES. 



The discovery that the Wolffian bodies become a part of the genital system was 

 made by Oken, through dissections and injections of dog embryos (Beitrage, Heft II> 



