Masseter

Origin, Insertion, Action & Nerve

Attachments explained

The Masseter 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 Masseter contracts, it produces the following movements: Elevates mandible (closes jaw); assists protraction.

As part of the Mastication group of the Head & Neck, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.

Nerve supply & clinical relevance

The Masseter receives its nerve supply from the Mandibular division of trigeminal nerve (CN V3).

Because a muscle can only contract when its nerve is intact, injury to the Mandibular division of trigeminal nerve can weaken or paralyse the Masseter, impairing the movements it normally produces (elevates mandible (closes jaw)). This is why knowing the innervation is central to localising nerve lesions in clinical practice.

How to study the Masseter (the OIANS method)

Learn the masseter as the classic jaw-closer you can feel yourself. Place your fingers over the angle of the mandible and clench, and the muscle springs up under your hand; that tangible bulge fixes both its insertion on the ramus and angle and its action of elevating the mandible. Reasoning from its near-vertical pull between the zygomatic arch and the mandibular angle makes its power in closing the bite intuitive.

Group the masseter with temporalis and the two pterygoids as the four muscles of mastication, all sharing supply from the mandibular division of the trigeminal nerve (CN V3). Anchoring this common innervation once covers the nerve for the whole group, leaving you free to distinguish the members by their differing actions on the mandible.

Frequently asked questions

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