The intermediate part of male urethra
) is the shortest, least dilatable, and, with the exception of the external orifice, the narrowest part of the canal.
It extends downward and forward, with a slight anterior concavity, between the apex of the prostate
and the bulb of the urethra
, perforating the urogenital diaphragm
about 2.5 cm. below and behind the pubic symphysis
The hinder part of the urethral bulb lies in apposition with the inferior fascia of the urogenital diaphragm, but its upper portion diverges somewhat from this fascia
: the anterior wall of the membranous urethra is thus prolonged for a short distance in front of the urogenital diaphragm; it measures about 2 cm. in length, while the posterior wall which is between the two fasciæ of the diaphragm is only 1.25 cm. long.
The membranous portion of the urethra is completely surrounded by the fibers of the Sphincter urethrae membranaceae
In front of it the deep dorsal vein of the penis
enters the pelvis
between the transverse ligament of the pelvis
and the arcuate pubic ligament
; on either side near its termination are the bulbourethral glands
Image:Illu penis.jpg|Structure of the penis
Image:Gray1156.png|Vertical section of bladder, penis, and urethra.
- - "The Female Pelvis: The Urethra"
- - "The Male Pelvis: The Urethra"