Anatomy, Abdomen and Pelvis: Ischioanal Fossa

Excerpt

The ischioanal fossa is also referred to as the ischiorectal fossa in some anatomy textbooks. The ischioanal fossa is a space filled with fat lateral to the anal canal and just below the pelvic diaphragm. The ischioanal fossa has a shape of a triangular pyramid with the apex at the boundary of the anal canal and the obturator fascia, and the base directed towards the perineal surface.

The ischioanal fossa is divided into the perianal space and the ischiorectal space by the perianal fascia. The perianal fascia is an extension of the insertion of the longitudinal muscles of the anal canal outwards between the subcutaneous external sphincter and the external sphincter muscle. This fascia extends across the ischiorectal fossa to the tuberosity of the ischium. The fat of the perianal space is closely packed and finely granular, while large lobules of avascular fat fill the ischiorectal space.