Anal Triangle

Anal triangle is the posterior part of the perineum that contains the anal canal and is defined by the following structures:

Vertices:

  • Posterior vertex is at the tip of coccyx bone
  • Two anterolateral vertices at the ischial tuberosities of the two hip bones

Borders:

  • Anterior border of the anal triangle is formed by the perineal membrane
  • The two posterolateral borders are formed by the sacrotuberous ligaments

Contents of anal triangle:

Anal triangle contains the following important components:

  • Ischiorectal fossa
  • Sacrotuberous ligament
  • Sacrospinous ligament
  • Pudendal nerve
  • Internal artery and vein
  • Anal canal
  • Various muscles including gluteus maximus, obturator internus, levator ani, and coccygeus

The anus, which is the lower opening of the anal canal, lies in the midline. On each side of it is the ischiorectal fossa. The skin around the anus is supplies by the inferior rectal nerve (hemorrhoidal nerve). The lymph vessels of this region of skin drain into the medial group of superficial inguinal lymph nodes.