- Layered musculotendinous structure between the Anal Canal and the caudal part of the vertebral column, on which the terminal Rectum sits
- From above downwards, it consists of:
- Superior Fascia of the Pelvic Diaphragm
- Tendinous Plate of Pubococcygeus
- Muscular Raphe of Iliococcygeus
- Posterior parts of Puborectalis and the External Anal Sphincter
- Nerve Supply:
- Main supply: Sacral Plexus by Branches of S3 and S4
- Enter the upper (pelvic) surface of the muscle
- Some fibres travel in or close to Pelvic Splanchnic Nerves
- Puborectalis, Pubourethralis, Pubovaginalis supplied from below by the Perineal Branch of S4 and Inferior Rectal Branch of Pudendal Nerve, in common with the External Anal Sphincter
- High proportion of slow twitch fibres (like the External Anal Sphincter and Urethral Sphincter muscles)