Iliococcygeus

Origin, Insertion, Action & Nerve

Attachments explained

The Iliococcygeus 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.

Action & function

When the Iliococcygeus contracts, it produces the following movement: Supports and elevates the pelvic floor and viscera.

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 Iliococcygeus receives its nerve supply from the Nerve to levator ani (anterior ramus of S4) and the pudendal nerve (S2–S4). This nerve carries fibres from spinal segment(s) S4, S2.

Because a muscle can only contract when its nerve is intact, injury to the Nerve to levator ani or to its spinal roots (S4, S2) can weaken or paralyse the Iliococcygeus, impairing the movements it normally produces (supports and elevates the pelvic floor and viscera). This is why knowing the innervation is central to localising nerve lesions in clinical practice.

How to study the Iliococcygeus (the OIANS method)

OIANS stands for Origin, Insertion, Action and Nerve, the four facts that uniquely define every skeletal muscle. To learn the Iliococcygeus, 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 Iliococcygeus 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.

Iliococcygeus quick facts

Region

Trunk

Group

Pelvis & Perineum

Origin

Ischial spine and posterior part of the tendinous arch of the obturator fascia

Insertion

Anococcygeal ligament (raphe) and coccyx

Action

Supports and elevates the pelvic floor and viscera

Nerve

Nerve to levator ani (anterior ramus of S4) and the pudendal nerve (S2–S4)

Spinal roots

S4, S2

Frequently asked questions

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