1120 UROGENITAL SYSTEM. 
the prostate is called the prostatic portion ; the short portion which pierces the pelvic 
wall is the membranous portion, and the part surrounded by the corpus spongiosum 
receives the name of spongy portion. Of these three sections of the urethra the 
spongy portion is much the longest, and the membranous is the shortest. 
Prostatic Portion of the Urethra. — The prostatic part (pars prostatica) 
of the urethra descends through the prostate from the base towards the apex, 
describing a slight curve which is concave forwards. It is about one inch 
in length, and is narrower above and below than in its middle portion, which is 
indeed the widest part of the whole urethral canal. Except while fluid is passing, 
the canal is collapsed, and the mucous membrane of the anterior and posterior walls 
is in contact, and thrown into a series of longitudinal folds. When distended, the 
middle, or widest part of the canal, may normally have a diameter of about one- 
third of an inch. The posterior wall, often termed the “floor” of the prostatic 
urethra, presents a distinct mesial ridge or 
elevation, called the crista urethre (crista 
urethralis) or verumontanum (Fig. 767). 
This projects forwards into the urethra to 
such an extent that the canal presents 
in transverse section a crescentic outline. 
In the depressions or grooves on each side 
of the crista urethre the numerous duets 
of the prostatic glands open by minute 
apertures. Some few ducts from the 
middle part of the gland open in the 
middle line, either just above or just 
below the urethral crest. On the summit 
of the crista urethree is a slit-like open- 
ing which leads backwards and upwards 
for a distance of about a quarter of an 
inch, as a blind pouch, in the substance of 
the prostate. This lttle' cavity is the 
prostatic utricle (utriculus prostaticus) or 
sinus pocularis, and represents the uterus 
/ and vagina of the female, being developed 
Fic. 767.— THE Prostatic, Mpmpranous, and from the fused posterior ends of the 
Urry FOUN oF Tue Stony Usk Midllerian duets. On each side of the 
posterior wall or floor. The minute openings mouth of the utricle is the much more 
of the common ejaculatory ducts and the orifice minute opening of the common ejaculatory 
eee pocularis are seen upon the crise duct. When traced upwards towaldsmgae 
bladder, the urethral crest, diminishing 
in height, becomes indistinct, but in some cases it can be traced as far as the uvula 
vesice. When followed in the opposite direction the ridge becomes less marked, 
and can be followed on the urethral wall into the membranous portion of the 
canal, where it divides into a pair of slight folds or elevations (Fig. 767). 
Membranous Part of the Urethra.— The second or membranous portion 
(pars membranacea) of the urethra leads downwards and forwards from the apex of 
the prostate to the bulb of the corpus spongiosum, and is the shortest and narrowest 
of the three subdivisions of the canal, its length being somewhat less than half 
an inch. It begins at the deep layer of the triangular ligament, where it is con- 
tinuous with the prostatic portion, and ends by piercing the superficial layer, to 
become continuous with the spongy portion of the urethra. Placed in front of the 
rectum, it lies about one inch behind and below the sub-pubie ligament, and is 
surrounded by fibres of the compressor urethree muscle. Behind it, on each side 
of the mesial plane, are Cowper’s glands. The membranous part of the urethra 
enters the bulb at a point somewhat in front of its posterior extremity, and, owing 
to the oblique direction of the canal as it joins the bulb, the anterior, or upper wall, 
of the passage is longer than the posterior wall or floor (Fig. 765). Further, the 
posterior part of the bulb projects so much backwards that it overlaps to a con- 
siderable extent the posterior wall of the second part of the urethra 
Bladder 
wall 
Prostate + ! 
Crista urethrie 
Cowper's gland 
Bulbus urethree 
Pars cavernosa__ 
urethree 
