The anal triangle is a part of the perineum located posterior to the urogenital triangle. It contains the anal canal, surrounded by a muscular external anal sphincter, with the fat-filled ischio-rectal fossa on each side. On each side of the anal canal, between the pelvic diaphragm and the obturator internus muscle is the wedge-shaped ischiorectal fossa.
The ischiorectal fossa is filled with fascia, containing a considerable amount of fat, which allows distension of the anal canal during defecation. The fossa is limited in front by the fascia of the superficial perineal pouch.