Puboanalis (Puborectalis)

Pelvis & Perineum · Trunk

Located in the Pelvis & Perineum of the Trunk, the Puboanalis (Puborectalis) is a key muscle for anatomy study. It arises from Posterior surface of the body of the pubis and attaches to Forms a U-shaped sling around the anorectal junction, joining its fellow. It is responsible for several movements: Maintains the anorectal angle for fecal continence; relaxes during defecation. Its nerve supply is 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)

OIANS stands for Origin, Insertion, Action and Nerve, the four facts that uniquely define every skeletal muscle. To learn the Puboanalis (Puborectalis), work through them in order: picture its origin, trace the muscle to its insertion, reason out the action that shortening between those two points must create, then add the nerve that drives it.

Most students remember the Puboanalis (Puborectalis) fastest by linking its action back to its attachments rather than memorising each fact in isolation. Once the origin and insertion make sense, the action usually follows logically.