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The perineal membrane is an
anatomical Anatomy () is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old science, having its ...
term for a fibrous
membrane A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Membranes can be generally classified into synthetic membranes and biological membranes. ...
in the
perineum The perineum in humans is the space between the anus and scrotum in the male, or between the anus and the vulva in the female. The perineum is the region of the body between the pubic symphysis (pubic arch) and the coccyx (tail bone), inclu ...
. The term "inferior fascia of
urogenital diaphragm Older texts have asserted the existence of a 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 ...
", used in older texts, is considered equivalent to the perineal membrane. It is the superior border of the
superficial perineal pouch The superficial perineal pouch (also superficial perineal compartment/space/sac) is a compartment of the perineum. Structure The superficial perineal pouch is an open compartment, due to the fact that anteriorly, the space communicates freely wi ...
, and the inferior border of the
deep perineal pouch The deep perineal pouch (also deep perineal space) is the anatomic space enclosed in part by the perineum, and located superior to the perineal membrane. Structure The deep perineal pouch is bordered inferiorly by the perineal membrane, also kno ...
.


Structure

The perineal membrane is triangular in shape. It attaches to both ischiopubic rami of the
pelvis The pelvis (plural pelves or pelvises) is the lower part of the trunk, between the abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also called bony pelvis, or pelvic skeleton). The ...
. It also attaches to the
perineal body The perineum in humans is the space between the anus and scrotum in the male, or between the anus and the vulva in the female. The perineum is the region of the body between the pubic symphysis (pubic arch) and the coccyx (tail bone), inclu ...
. It is about 4 cm. in depth. Its apex is directed forward, and is separated from the arcuate pubic ligament by an oval opening for the transmission of the deep dorsal vein of the penis or the deep dorsal vein of the clitoris. Its lateral margins are attached on either side to the inferior rami of the pubis and
ischium The ischium () form ...
, above the
crus penis For their anterior three-fourths the corpora cavernosa penis lie in intimate apposition with one another, but behind they diverge in the form of two tapering processes, known as the crura, which are firmly connected to the ischial rami. Traced ...
. Its base is directed toward the
rectum The rectum is the final straight portion of the large intestine in humans and some other mammals, and the gut in others. The adult human rectum is about long, and begins at the rectosigmoid junction (the end of the sigmoid colon) at the l ...
, and connected to the central tendinous point of the
perineum The perineum in humans is the space between the anus and scrotum in the male, or between the anus and the vulva in the female. The perineum is the region of the body between the pubic symphysis (pubic arch) and the coccyx (tail bone), inclu ...
. The base is fused with both the pelvic fascia and Colle's fascia.


Relations

It is continuous with the deep layer of the
superficial fascia A fascia (; plural fasciae or fascias; adjective fascial; from Latin: "band") is a band or sheet of connective tissue, primarily collagen, beneath the skin that attaches to, stabilizes, encloses, and separates muscles and other internal organs ...
behind the superficial transverse perineal muscle, and with the inferior layer of the diaphragmatic part of the pelvic fascia.


Perforations

It is perforated, about 2.5 cm. below the
pubic symphysis The pubic symphysis is a secondary cartilaginous joint between the left and right superior rami of the pubis of the hip bones. It is in front of and below the urinary bladder. In males, the suspensory ligament of the penis attaches to the pubi ...
, by the
urethra The urethra (from Greek οὐρήθρα – ''ourḗthrā'') is a tube that connects the urinary bladder to the urinary meatus for the removal of urine from the body of both females and males. In human females and other primates, the urethra ...
, the aperture for which is circular and about 6 mm. in diameter, by the arteries to the bulb, and the ducts of the bulbourethral glands close to the urethral orifice; by the deep arteries of the penis, one on either side close to the pubic arch, and about halfway along the attached margin of the fascia; by the dorsal arteries and nerves of the penis near the apex of the fascia. Its base is also perforated by the perineal vessels and nerves, while between its apex and the arcuate pubic ligament the deep dorsal vein of the penis passes upward into the pelvis.


Contents

If the inferior fascia of the urogenital diaphragm is detached on either side, the following structures will be seen between it and the superior fascia: * the deep dorsal vein of the penis * the membranous portion of the urethra * the deep transverse perineal muscle and the urethral sphincter muscles * the bulbourethral glands and their ducts * the pudendal arteries and dorsal nerves of the penis * the arteries and nerves of the urethral bulb * a plexus of
veins Veins are blood vessels in humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated ...


Additional images

Image:Gray1154.png, The constituent cavernous cylinders of the penis.


References


External links

* (, ) {{Authority control Perineum