THE URETHRA. 



1923 



sinus is, therefore, regarded as the morphological equivalent of the vagina and uterus. 

 On the lateral lips of this recess lie the small orifices of the ejaculatory ducts, while 

 those of the prostatic tubules open into the groove-like depressions on either side of 

 the urethral crest. The internal urethral orifice lies approximately on a horizontal 

 plane passing through the middle of the symphysis, about 2.5 cm. (i in.) behind 

 the latter and an equal distance from its lower border. 



The membranous portion (pars membranacea) curves downward and forward 

 from the apex of the prostate to the bulb of the corpus spongiosum, which it enters 

 somewhat (about i cm. ) in advance of its posterior extremity. In its course the 

 membranous urethra pierces both layers of the triangular ligament and is surrounded 

 by the fibres of the compressor urethrae muscle ; behind it, on either side of the 

 mid-line, lie the glands of Cowper. This part of the canal measures only about i cm. 

 in length, and is the shortest, narrowest, and least distensible of the segments. 

 When empty, its mucous membrane is thrown into longitudinal folds, and on cross- 

 section its lumen is stellate. In 



consequence of its curved course, 

 the anterior wall is shorter than the 

 posterior, which marks the most 

 dependent point of the subpubic 

 curve that lies about 1 8 mm. ( 3^ 

 •in. ) below and behind the lower 

 border and in the plane of the sym- 

 physis. Since almost the entire 

 membranous portion lies between 

 the layers of the triangular liga- 

 ment, its mobility is much less 

 than that of the other parts of the 

 urethra. The short terminal part 

 of the membranous urethra that 

 lies below the triangular ligament 

 and above and in front of the bulb 

 as it enters the corpus spongiosum 

 (pars praetrigonalis) is, however, 

 not only wider and thin-walled, 

 but much more movable, — charac- 

 teristics that increase the difificulty 

 of guiding instruments into the 

 narrow and fixed intratrigonal seg- 

 ment beyond. 



The spongy portion (pars 

 cavernosa) includes the remainder 

 of the canal and terminates at 

 the external urethral orifice. Its 

 length varies with the size and 



Fig. 1632, 



Vesical trigone 



Ejaculatory duct 



Opening 



of left 

 ureter 



Bladder wall, cut 



Urethral crest 



Prostatic utricle 

 Prostate, cut 



Membranous urethra 



Bulbus 

 spongiosum 



Spongy urethra 



Cowper's gland 



Opening of duct of 

 Cowper's gland 



ij Corpus 



cavernosum, cut 

 and turned out 



Part of bladder and male urethra, exposed by opening and 

 turning aside anterior wall, showing posterior surface of prostatic, 

 membranous, and beginning of spongy portions of urethra. 



vanes 

 condition of the penis, but averages about 14 cm. (51^ in.). In the flaccid condi- 

 tion of the penis it presents a double curve (Fig. 16 19), the fixed proximal part of 

 which continues the subpubic curve forward and slightly upward through the peri- 

 neum to a point corresponding approximately with the attachment of the suspensory 

 ligament to the dorsum of the penis, while the freely movable distal part, ox prepubic 

 curve, follows the pendent penis. Throughout its course this part of the urethra is 

 surrounded by the corpus spongiosum, at first embedded near its upper border, then 

 about in the middle, and at the termination near its lower margin covered by the 

 thick cap of spongy substance forming the glans. The lumen of the spongy portion 

 is variable both in size and form ; at its two ends, where surrounded by the bulb and 

 the glans, it presents fusiform dilatations, the intermediate part being of more uniform 

 calibre. The first of these dilatations (fossa bulbi) occupies the bulb of the corpus 

 spongiosum for about 2 cm., beginning about half that distance in front of its posterior 

 extremity. Abruptly narrowing behind, towards the pars membranacea, in front the 

 fossa gradually diminishes into the ordinary lumen of the canal. The ducts of Cow- 



