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Urogenital Diaphragm

The Urogenital diaphragm is a superficial muscular membrane that separates the deep perineal sac from the upper pelvis.


The urogenital diaphragm is a triangle shaped muscle layer created by sphincter urethrae along with deep transverse perineal muscles. They are confined among a superior as well as an inferior layer of fascia of the urogenital diaphragm. The inferior layer of fascia is often called as the perineal membrane.


  • Anteriorly, the two layers of fascia merge, leaving behind a small space beneath the symphysis pubis.
  • Posteriorly, the two layers of fascia fuse with each other as well as with the membranous layer of the superficial fascia along with the perineal body.
  • Laterally, the layers of fascia are connected to the pubic arch.
  • The confined space which is enclosed among the superficial and deep layer of fascia is called the deep perineal pouch.

On the deeper part it is wrapped by a thin layer of endopelvic fascia referred to as superior fascia of the urogenital diaphragm, and on the superficial part it is enveloped by the perineal membrane named inferior fascia of the urogenital diaphragm. It is perforated by the urethra in male and via the urethra and vagina in female, and also consists of bulbourethral glands inside it in male. This triangular diaphragm holds the urogenital triangle with its top behind the pubic symphysis along with its sides connected to the ischiopubic rami.


It has two fasciae called

  • Inferior layer of the diaphragm or the perineal membrane.
  • Superior layer of the diaphragm.

Perineal Membrane

It is also referred to as the deep fascia of the perineum or inferior layer of the diaphragm.


  • At sides: to the pubic arch.
  • Posteriorly: Over the transversus perinei superficialis, it merges along with the fascia of Colies. Over the transversus perinei profundus, it merges along with the superior layer of the urogenital diaphragm.
  • Anteriorly: It terminates within a free thickened periphery called transverse perineal ligament which is divided via the inferior pubic ligament by a space where deep dorsal vein of the penis passes within male to terminate in the prostatic venous plexus or deep dorsal vein of the clitoris within female in order to terminate within the vesical venous plexus.

Superior Layer of the Diaphragm

It is Triangle shaped.


  • Anteriorly: It merges along with the transverse perineal ligament.
  • Posteriorly: Around the transversus perinei profundus; it blends along with the perineal membrane.
  • At sides: To the pubic arch.
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