- Anal canal: terminal part of the large intestine (3.8 cm long), in the perineum below the pelvic diaphragm.
- Kept closed by an inner involuntary and outer voluntary sphincter except during defecation.
Location, Extent and Relations
- Location: anal triangle of the perineum, between the ischiorectal fossae.
- Extent: anorectal junction to the anal orifice, in the natal cleft, about 4 cm below and in front of the coccyx tip.
- Course: passes downward and backward; puborectalis pulls the anorectal junction forward, producing a 90-degree perineal flexure.
- Skin around the anal orifice is pigmented, thrown into radiating folds by the corrugator cutis ani.
Relations of the anal canal