THE REPRODUCTIVE SYSTEM 347 



and a lining epilhclium. The epithelium is of the stratified columnar 

 type with two or three rows of cells, being similar to that lining the 

 vas epididymis. The extent to which the epithelium is ciliated 

 varies greatly^. In some cases the entire vas is ciliated, in others only 

 the upper portion, in still others no cilia are present beyond the epi- 

 didymis. The epithelium rests upon a basement membrane beneath 

 which is a fibro-elastic cellular stroma. The stroma merges without 

 distinct demarcation into the more vascular suhmucosa. 



^*» o 



\ 



-6 



C 



■ d 



^^^. e 



Fig. 243. — Cross Section of Human Vas Deferens. X37. (Szymonowicz.) a, 

 Epithelium; h, stroma; c, submucosa; d, inner circular muscle layer; c, outer longitudinal 

 muscle layer;/, fibrous layer; g, blood-vessels. 



The miiscularis consists of two strongly developed layers of smooth 

 muscle, an inner circular and an outer longitudinal (Fig. 243), which 

 together constitute about seven-eighths of the wall of the vas. At 

 the beginning of the vas deferens a third layer of muscle is added 

 composed of longitudinal bundles, and situated between the inner' 

 circular layer and the submucosa. 



The fibrosa consists of fibrous tissue containing many elastic 

 fibres. 



Near its termination the vas dilates to form the ampulla, the 

 walls of which present essentially the same structure as those of the 

 vas. The lining epithelium is, however, frequently markedly pig- 

 mented and the mucosa contains branched tubular glands. 



