The innervation of the muscles of continence.

Electrophysiological evidence is presented that suggests that the innervation of the human puborectalis muscle differs from that of the external anal sphincter muscle. The latter is innervated by branches of the pudendal nerves, and the former by direct branches of the sacral plexus that enter the muscle from its pelvic surface. The striated urinary sphincter musculature also receives a dual innervation. The periurethral component is innervated by perineal branches of the pudendal nerves and the intramural portion by a different pathway, probably consisting of supralevator branches derived from the pelvic nerves. These findings are relevant to understanding the embryological derivation of these muscles and have practical importance in the surgery of this region of the body, particularly in the treatment of incontinence.