Anatomy, Abdomen and Pelvis: Anal Triangle

The anal triangle is the posterior half of the perineum, by definition. The perineum can be found between the thighs and below the pelvic diaphragm. The perineum is comprised of the anal and urogenital triangles. A theoretical line connecting the two ischial tuberosities of the pelvis divides the perineum into the posterior anal triangle and anterior urogenital triangle.

The anal triangle is formed by the coccyx, sacrotuberous ligaments, and an imaginary line between the ischial tuberosities. The anal triangle contains the anal canal and two ischiorectal (ischioanal) fossae that lie on either side of the anal canal.

Boundaries of the anal triangle:

1. Anterior: posterior margin of the perineal membrane

2. Posterior: coccyx

3. Posterolateral: sacrotuberous ligaments

4. Superior: levator ani muscle