43 ABDOMEN 



part, pars cavernosa urethra, traverses the entire length of the 

 corpus cavernosum urethras. 



Pars Prostatica Urethras. The prostatic part of the 

 urethra is about 30 mm. (one inch and a quarter) in 

 length. It is fusiform, being wider in the middle than at 

 either its commencement or its termination. It traverses 

 the prostate in front of its so-called middle lobe, and takes 

 a very nearly vertical course through the substance of the 

 prostate. It is the widest, and at the same time the most 

 dilatable, part of the canal. 



In connection with the posterior wall or floor of the prostatic 

 portion of the urethra there are certain important features 

 to be noted. The mucous membrane along the median plane 

 is raised into a prominent ridge called the crista urethra. 

 The urethral crest commences a short distance below the 

 internal orifice of the urethra, and extends downwards for 

 about three-quarters of an inch. At first it increases gradu- 

 ally in height, until it forms a prominent eminence, the 

 colliculus seminalis or seminal hillock ; then its height 

 suddenly diminishes, and, finally, the ridge fades away into 

 the membranous part of the canal (Fig. 200). On each side of 

 the urethral crest the floor of the urethra is a longitudinal de- 

 pression, termed the prostatic sinus, into which the numerous 

 prostatic ducts open. The dissector may render the prostatic 

 ducts evident by squeezing the prostate, when fluid will be 

 found to exude into the sinuses through the ducts. A 

 close inspection of the floor of the urethra, above the crista, 

 will reveal the apertures of the ducts of the so-called middle 

 lobe of the prostate. 



Immediately below the seminal hillock the mucous 

 membrane dips backwards and upwards, forming a small cul- 

 de-sac, the utriculus prostaticu s, behind the middle lobe of the 

 prostate (Fig. 203). The orifice of the prostatic utricle is 

 narrow, but the recess widens out towards its blind upper 

 end, and its length, which may be gauged with a probe, varies 

 from 6 to 1 2 mm. (a quarter to half an inch). It is of interest 

 both practically and developmentally, practically, because it 

 is sometimes large enough to entangle the point of a small 

 catheter or bougie ; and developmentally, because it repre- 

 sents, in the male, the vagina and uterus of the female. 



On the margins of the orifice of the prostatic utricle the 

 dissector will find the slit -like orifices of the ejaculatory 



