1976 



HUMAN ANATOMY. 



FIG. 1680. 



Prostate, middle lobe 

 Ejaculatory duct 



Inferior wall 

 of bladder 



Internal urethral 

 orifice 



Urethral crest-^ 



Prostatic urethra 



Portion of sagittal section showing prostate and related structures. 



that often presents a shallow concavity. The junction of the upper and posterior 

 surfaces is marked lv a transverse crescentic slit (incisura prostatae) into which sink 

 the eiaculatory ducts in their course to the urethra. The imperfectly defined wedge- 



shaped mass bounded by 

 the urethra in front, the ejac- 

 ulatory ducts at the sides 

 and behind, constitutes the 

 so-called middle lobe (lobus 

 niedius), the base of which 

 lies beneath the vesical tri- 

 gone. The prominent por- 

 tions of the prostate lying 

 external to the ejaculatory 

 ducts are known as the lat- 

 eral lobes, which, however, 

 superficially are not dis- 

 tinctly marked off. The 

 prominent convex lateral 

 surfaces, directed outward, 

 downward, and forward, and 

 behind limited by rounded 

 borders, in front pass insen- 

 sibly into the narrow con- 

 vex anterior surface (facies 

 anterior) that is approximately vertical and faces the symphysis. 



The urethra traverses the prostate with a vertically placed curve, the concavity 

 looking forward, that above begins slightly in advance of the middle of the base, and 

 below ends on the anterior surface just in front and above the apex. The posterior 

 wall of the prostatic urethra is marked by a longitudinal median ridge, the urethral 

 crest, on the most expanded and elevated part of which (colliculus seminalis) are situ- 

 ated the openings of the pros- 

 tat ii -utricle ( utriculus prostati- FlG - l6Sl - 

 cus) and of the ejaculatory 

 ducts (page 1955). In the 

 grooves or recesses on either 

 side of the crest, open the mi- 

 nute orifices of the prostatic tu- 

 bules, some twenty in number, 

 that discharge the products of 

 the glandular tissue. 



Owing to the continuity 

 of the muscular tissue with 

 the surrounding structures in 

 front, above, and below, the 

 outlines of the prostate in 

 plan-slack definition. Except 

 over its base, apex, and lower 

 anterior surface, the prostate 

 is enclosed by a fibrous envel- 

 ope or fuf>sn/t\ the extension 

 of the visceral layer of the pel- 

 vic fascia in conjunction with 

 the investment of the bladder 

 and the seminal vesicles. The 



C.I|>Mlle i- liest developed Oil 



the posterior surface, when- it separates the prostate from the rectum and constitutes 

 a part of tin- recto \ epical fascia in its restricted sense. 



Relations. Lodged between the bladder and the pelvic floor, the prostate is 

 in relation with a number of important structures. Above, its base is intimately 



Folds of 

 mucous membrane 



Lume 



Urethral mucous 



membrane 



1 crest 



utricle 



Ejaculatory ducts 



Section across prostatic urethra above entrance of ejacula- 

 tory ducts, showing crescentic form of urethral lumen pro- 

 duced by encroachment of urethral crest. X 10. 



