Puboanalis (Puborectalis)
Pelvis & Perineum · Trunk
The puboanalis, better known in its stronger form as the puborectalis, is the most medial and functionally distinctive part of the levator ani. It arises from the posterior surface of the body of the pubis and, instead of inserting onto bone, passes backward on each side to form a U-shaped sling that loops around the anorectal junction and joins its fellow behind the rectum. This sling pulls the anorectal junction forward, creating the anorectal angle that is critical for maintaining fecal continence; during defecation the muscle relaxes, the angle straightens, and the rectum empties. It is supplied by the nerve to levator ani (S3-S4).
Origin, Insertion, Action & Nerve
Origin
Posterior surface of the body of the pubis
Insertion
Forms a U-shaped sling around the anorectal junction, joining its fellow
Action
Maintains the anorectal angle for fecal continence; relaxes during defecation
Nerve
Nerve to levator ani (S3–S4)
Attachments explained
The Puboanalis (Puborectalis) is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.
Origin
Posterior surface of the body of the pubis
Insertion
Forms a U-shaped sling around the anorectal junction, joining its fellow
Action & function
When the Puboanalis (Puborectalis) contracts, it produces the following movements: Maintains the anorectal angle for fecal continence; relaxes during defecation.
As part of the Pelvis & Perineum group of the Trunk, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.
Nerve supply & clinical relevance
The Puboanalis (Puborectalis) receives its nerve supply from the Nerve to levator ani (S3–S4). This nerve carries fibres from spinal segment(s) S3, S4.
Because a muscle can only contract when its nerve is intact, injury to the Nerve to levator ani or to its spinal roots (S3, S4) can weaken or paralyse the Puboanalis (Puborectalis), impairing the movements it normally produces (maintains the anorectal angle for fecal continence). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Puboanalis (Puborectalis) (the OIANS method)
Picture the puborectalis literally as a sling: it leaves the pubis, wraps behind the anorectal junction, and returns to the pubis, kinking the gut forward. That single mental image explains both its normal job, holding the anorectal angle acute for continence, and how it works, relaxing to open the angle so stool can pass. It is the one levator ani part that does not attach to the coccyx, which is a reliable way to distinguish it.
Contrast the puborectalis with the external anal sphincter to avoid confusion: the sphincter squeezes the anal canal shut, while the puborectalis kinks the bowel above it, and the two work together for continence. Remember that continence testing and biofeedback often assess the anorectal angle it creates, and its nerve to levator ani (S3-S4) keeps it grouped with the rest of the pelvic diaphragm.
Frequently asked questions
Where is the Puboanalis (Puborectalis) located?
The Puboanalis (Puborectalis) is a muscle of the Pelvis & Perineum group, located in the Trunk.
What is the origin of the Puboanalis (Puborectalis)?
Posterior surface of the body of the pubis
What is the insertion of the Puboanalis (Puborectalis)?
Forms a U-shaped sling around the anorectal junction, joining its fellow
What movements does the Puboanalis (Puborectalis) produce?
Maintains the anorectal angle for fecal continence; relaxes during defecation
What nerve supplies the Puboanalis (Puborectalis)?
Nerve to levator ani (S3–S4)
Is the Puboanalis (Puborectalis) free to study in OIANS?
The Puboanalis (Puborectalis) is always free to browse. Its full origin, insertion, action and nerve details are open to everyone in the Muscle Directory. Quiz and Flashcard practice for the Trunk is part of the one-time Lifetime upgrade, though; only the Upper Limb decks are free to test yourself on.
Related muscles
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