In the rat, m. anococcygeus appears as a paired smooth muscle. In the males the muscle divides into a dorsal and ventral part. The ventral parts from both sides embrace the rectum ventrocaudally, they join in front of the rectum and proceed in the septum scroti in a fan-like manner. The dorsal part of the muscle in males and the whole muscle in the females proceed caudally along the lateral gut circumference, gradually developing a fibromuscular plate, a cord adjoining the rectal wall. Caudally from the junction of MA, the longitudinal gut musculature is more abundant in the plate area, appearing as if extracted in the form of a longitudinal column. Directed towards the anus, a frontally oriented septum is formed from connective tissue emerging from the columns. The morphology of the muscle as described here permits to assume that MA in the females and its dorsal part in the males operates as a levator ani, the ventral part of the muscle in males operating as a levator - retractor scroti.

Department of Anatomy Faculty of General Medicine Charles' University Prague Czechoslovakia