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SPLANCHNOLOGY 



The Male Urethra (Urethra Virilis) (Fig. 1142). 



The male urethra extends from the internal urethral orifice in the urinary bladder 

 to the external urethral orifice at the end of the penis. It presents a double curve 

 in the ordinary relaxed state of the penis (Fig. 1137). Its length varies from 17.5 

 to 20 cm.; and it is divided into three portions, the prostatic, membranous, and 



cavernous, the structure and rela- 

 tions of which are essentially 

 different. Except during the 

 passage of the urine or semen, 

 utricle the greater part of the urethral 

 and ejaculatory ducts canal is a mere transverse cleft 

 Prostatic part of urethra Qr ^ wjth itg upper an( j un( j er 



surfaces in contact; at the external 

 orifice the slit is vertical, in the 

 membranous portion irregular or 

 stellate, and in the prostatic por- 

 tion somewhat arched. 



The prostatic portion (pars pros- 

 tatica), the widest and most dila- 

 table part of the canal, is about 

 3 cm. long, It runs almost ver- 

 tically through the prostate from 

 its base to its apex, lying nearer 

 its anterior than its posterior 

 surface; the form of the canal 

 is spindle-shaped, being wider in 

 the middle than at either extrem- 

 ity, and narrowest below, where 

 it joins the membranous portion. 

 A transverse section of the canal 

 as it lies in the prostate is horse- 

 shoe-shaped, with the convexity 

 directed forward. 



Upon the posterior wall or 

 floor is a narrow longitudinal 

 ridge, the urethral crest (vern- 

 montanum), formed by an eleva- 

 tion of the mucous membrane 

 and its subjacent tissue. It is 

 from 15 to 17 mm. 'in length, 

 and about 3 mm. in height, and 



contains, according to Kobelt, muscular and erectile tissue. When distended, 

 it may serve to prevent the passage of the semen backward into the bladder. 

 On either side of the crest is a slightly depressed fossa, the prostatic sinus, the floor 

 of which is perforated by numerous apertures, the orifices of the prostatic ducts 

 from the lateral lobes of the prostate; the ducts of the middle lobe open behind 

 the crest. At the forepart of the urethral crest, below its summit, is a median 

 elevation, the colliculus seminalis, upon or within the margins of which are the 

 orifices of the prostatic utricle and the slit-like openings of the ejaculatory ducts. 

 The prostatic utricle (sinus pocularis) forms a cul-de-sac about 6 mm. long, which 

 runs upward and backward in the substance of the prostate behind the middle 

 lobe. Its walls are composed of fibrous tissue, muscular fibers, and mucous 



Small lacuna 



Lacuna magna 



Ext. urethra! orifice 



FIG. 1142. The male urethra laid open on its anterior (upper) 

 surface. 



