Coccygeus
Pelvis & Perineum · Trunk
The coccygeus, also called the ischiococcygeus, is the smaller and more posterior of the two muscles forming the pelvic floor, lying behind the levator ani. It arises from the ischial spine and the closely applied sacrospinous ligament, with which it shares the same triangular outline, and inserts onto the lateral margin of the coccyx and the lowest part of the sacrum. Together with the levator ani it supports the pelvic viscera, and it also pulls the coccyx forward to restore its position after it has been pushed back during defecation or childbirth. It is supplied by the anterior rami of the fourth and fifth sacral nerves.
Origin, Insertion, Action & Nerve
Origin
Ischial spine and sacrospinous ligament
Insertion
Lateral margin of the coccyx and lowest part of the sacrum
Action
Supports the pelvic viscera and pulls the coccyx forward after defecation
Nerve
Anterior rami of S4–S5
Attachments explained
The Coccygeus 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
Ischial spine and sacrospinous ligament
Insertion
Lateral margin of the coccyx and lowest part of the sacrum
Action & function
When the Coccygeus contracts, it produces the following movement: Supports the pelvic viscera and pulls the coccyx forward after 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 Coccygeus receives its nerve supply from the Anterior rami of S4–S5. This nerve carries fibres from spinal segment(s) S4, S5.
Because a muscle can only contract when its nerve is intact, injury to the Anterior rami of S4–S5 or to its spinal roots (S4, S5) can weaken or paralyse the Coccygeus, impairing the movements it normally produces (supports the pelvic viscera and pulls the coccyx forward after defecation). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Coccygeus (the OIANS method)
Learn the coccygeus alongside the levator ani as the two components of the pelvic diaphragm, but distinguish it by its posterior position and its intimate relationship with the sacrospinous ligament, which lies flat against its pelvic surface. Because it stretches from the ischial spine to the coccyx, both its supporting role and its ability to draw the coccyx forward follow directly from its attachments.
Remember its dual name, ischiococcygeus, as a built-in map of origin and insertion, from the ischial spine to the coccyx. Its supply by the sacral anterior rami of S4 and S5 places it firmly within the pelvic floor group, so linking the muscle, the sacrospinous ligament, and those low sacral nerve roots as a set makes it easy to recall on exams.
Frequently asked questions
Where is the Coccygeus located?
The Coccygeus is a muscle of the Pelvis & Perineum group, located in the Trunk.
What is the origin of the Coccygeus?
Ischial spine and sacrospinous ligament
What is the insertion of the Coccygeus?
Lateral margin of the coccyx and lowest part of the sacrum
What movements does the Coccygeus produce?
Supports the pelvic viscera and pulls the coccyx forward after defecation
What nerve supplies the Coccygeus?
Anterior rami of S4–S5
Is the Coccygeus free to study in OIANS?
The Coccygeus 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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