196 NORMAL HISTOLOGY. 



ceive their blood from the rich capillary system lying 

 in the mucosa beneath the epithelium. This venous 

 net-work is so dense and the vessels so large as to 

 lend to the submucosa, especially in the prostatic 

 and membranous portions, the character of erectile 

 tissue (see below). 



Here and there, in the spongy portion, larger and 

 smaller irregular depressions, called lacunce Morgagni, 

 are seen in the surface of the mucous membrane. 

 Racemose glands, called Littres glands, lie imbed- 

 ded in the mucous membrane, sometimes extending 

 into the muscular tunic ; their excretory ducts, some- 

 times short, sometimes long and tortuous, open on 

 the surface of the mucous membrane. In the pros- 

 tatic portion, the prostatic and ejaculatory ducts 

 pierce the mucous membrane, as do the ducts of 

 Cowper's glands that of the posterior segment of the 

 spongy portion. 



The muscular tunic of the urethra consists, in 

 general, of an inner longitudinal and an outer circu- 

 lar layer of smooth muscle-cells, but varies greatly 

 in structure in the different portions. The outer 

 layers of the posterior portion of the canal are 

 formed, in part, of striated muscle. The musculosa 

 or the spongy portion consists entirely of smooth 

 muscle-cells, and forms a complete circular layer in 

 the posterior region alone, while anteriorly only 

 scattered, transversely and obliquely placed cells are 

 found. 



