 It arises by tendinous fibers from the inner and forepart of the ischial tuberosity and, running medially, is inserted into the central tendinous point of the perineum (perineal body), joining in this situation with the muscle of the opposite side, with the external anal sphincter muscle behind, and with the bulbospongiosus muscle in front.In some cases, the fibers of the deeper layer of the external anal sphincter cross over in front of the anus and are continued into this muscle.Occasionally it gives off fibers, which join with the bulbocavernosus of the same side.