Nerve · Pelvis

Nerve to levator ani

Nervus musculi levatoris ani

A direct branch of the sacral plexus, usually from S3 and S4, that drops onto the upper — pelvic — surface of the levator ani and supplies it from above. This matters because the pelvic floor has two nerve supplies approaching from opposite sides: this one from within the pelvis, and branches of the pudendal nerve arriving from the perineum below. Twigs from the same S3–S4 level also reach coccygeus behind it. A muscle that has to hold the weight of the abdominal contents is wired redundantly, and this is the upper half of that redundancy.