Perineum

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The perineum

The perineum is a diamond-shaped area that lies inferior to the pelvic diaphragm in the pelvis. Its borders are:

  1. tip of the coccyx
  2. sacro-tuberous ligaments
  3. ischial tuberosities
  4. ischio-pubic rami
  5. pubic symphysis

The perineum can be divided into two triangles by a line joining the two ischial tuberosities. The anterior division is the urogenital triangle and the posterior division is the anal triangle.

The veins of the right half of the male pelvis.

Internal pudendal vessels

The artery is derived from the internal iliac arteries and has branches corresponding to those of the pudendal nerve. Some of the branches to the penis/clitoris supply the erectile tissue.

The internal pudendal vein ultimately drains to the internal iliac vein but it has tributaries that also anastomose with other veins. The deep dorsal vein of the penis, draining the erectile tissue, passes through the anterior deficiency in the urogenital diaphragm, to join the prostatic plexus. Superficial structures of the perineum (e.g., vulva and scrotum) are also supplied and drained by external pudendal vessels, which are branches and tributaries of the femoral artery and vein.

Lymphatics

Superficial structures, including the vulva, lower part of the anal canal, scrotum and skin of the penis/clitoris drain with superficial vessels to superficial inguinal nodes. Deeper structures of the penis and clitoris drain ultimately to internal iliac nodes, while the upper part of the anal canal follows the superior rectal vessels to inferior mesenteric nodes.

Objectives

  • state its location with reference to specific landmarks
  • define the terms "urogenital" and "anal" triangle
  • with respect to the urogenital triangle, define the terms superficial and deep perineal pouch , list their contents and state their functions
  • list the differences between male and female superficial and deep perineal pouches
  • with respect to the anal triangle, describe the anal canal and the structure and function of the external anal sphincter
  • describe the course of the pudendal nerve, its distribution and functions
  • describe the course of the internal pudendal vessels and their areas of supply and drainage

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