Anatomy

Origin

It arises from the central tendinous point of the perineum and from the median raphe in front.    

Nerve

Perineal branch of the pudendal nerve.

Actions

This muscle serves to empty the canal of the urethra, after the bladder has expelled its contents; during the greater part of the act of micturition its fibers are relaxed, and it only comes into action at the end of the process. The middle fibers are supposed by Krause to assist in the erection of the corpus cavernosum urethrae, by compressing the erectile tissue of the bulb. The anterior fibers also contribute to the erection of the penis by compressing the deep dorsal vein of the penis as they are inserted into, and continuous with, the fascia of the penis.