Membranous urethra
Encyclopedia
The intermediate part of male urethra (membranous portion) 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.
It extends downward and forward, with a slight anterior concavity, between the apex of the prostate
Prostate
The prostate is a compound tubuloalveolar exocrine gland of the male reproductive system in most mammals....
and the bulb of the urethra, perforating the urogenital diaphragm
Urogenital diaphragm
Older texts have asserted the existence of an urogenital diaphragm, also called the triangular ligament, which was described as a layer of the pelvis that separates the deep perineal sac from the upper pelvis, lying between the inferior fascia of the urogenital diaphragm and superior fascia of the...
about 2.5 cm. below and behind the pubic symphysis
Pubic symphysis
The pubic symphysis or symphysis pubis is the midline cartilaginous joint uniting the superior rami of the left and right pubic bones. It is located anterior to the urinary bladder and superior to the external genitalia; for females it is above the vulva and for males it is above the penis...
.
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
Fascia
A fascia is a layer of fibrous tissue that permeates the human body. A fascia is a connective tissue that surrounds muscles, groups of muscles, blood vessels, and nerves, binding those structures together in much the same manner as plastic wrap can be used to hold the contents of sandwiches...
: 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
Deep dorsal vein of the penis
The deep dorsal vein of the penis lies beneath the deep fascia of the penis; it receives the blood from the glans penis and corpora cavernosa penis and courses backward in the middle line between the dorsal arteries; near the root of the penis it passes between the two parts of the suspensory...
enters the pelvis
Pelvis
In human anatomy, the pelvis is the lower part of the trunk, between the abdomen and the lower limbs .The pelvis includes several structures:...
between the transverse ligament of the pelvis and the arcuate pubic ligament; on either side near its termination are the bulbourethral glands.