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Common Urological Problems

Perineum

  • - Female Urology & Urogynecology - Anatomy of Pelvic Support
  • Jun 19, 2010
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Tags: | anal sphincter | anus | bartholin gland | bony pelvis |

The anatomic boundaries of the perineum are the pubis, thighs, and buttocks and can be divided into an anterior urogenital and a posterior anal triangle by drawing a line between the ischial tuberosities (Fig. 3) (7).

The perineal body is a tendinous structure in the midline of the perineum between the anus and the vaginal introitus, which provides a central point of fixation for the superficial transverse perineal muscle, the striated urogenital sphincter (formerly the deep transverse perineal muscle), the bulbocavernosus muscles anteriorly, and the external anal sphincter posteriorly (3).  The perineal membrane, formerly the urogenital diaphragm, refers principally to the deep transverse perineal muscles and associated superior and inferior fascia.

This fibromuscular sheet is triangular shaped, with openings for the urethra and vagina, and supports the anterior triangle. Voluntary contraction of the perineal membrane results in vaginal compression and provides stability to the perineum during periods of increased intrabdominal pressure.

The clitoris is located at the apex of the urogenital triangle and is composed of a glans, shaft, and crura. The shaft is anchored to the pubic bone by the suspensory ligament. The crura run posterolaterally along the pubic rami. The urogenital triangle is bordered laterally by the ischiocavernosus muscles,  which originate from the ischial tuberosities and the free posterior crura and insert onto the anterior crura and the body of the clitoris (3). The bulbocavernosus muscles run on each side of the vaginal vestibule beneath the labia majora from the pubis to the perineal body.

Fig. 14. Schematic diagram of normal uterine support. (From ref. 7.)Schematic diagram of normal uterine support

Beneath the bulbocavernosus muscles are the vestibular bulbs, which are highly vascular erectile tissue. The Bartholin gland is found at the inferior aspect of the bulb; therefore, care should be taken to minimize bleeding when dissecting in this area (3).

Of clinical significance,  a fibrous fat pad lies just beneath the skin of the labia majora, which can be used as a vascularized flap (Martius flap) when a multilayer vaginal closure is necessary.

Fig. 15. Schematic diagram of normal vaginal support. (From ref. 7.)Schematic diagram of normal vaginal support

The strength of the graft is derived from termination of the round ligament into the fibrofatty tissue. The flap can be based inferiorly off the inferior labial artery, a branch of the internal pudendal, or superiorly off the superficial external pudendal artery (10).

The posterior triangle is described briefly as it relates to posterior vaginal wall prolapse.

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