Digastric

Origin, Insertion, Action & Nerve

Attachments explained

The Digastric 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 Digastric contracts, it produces the following movements: Elevates hyoid bone; depresses mandible (opens jaw).

As part of the Neck 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 Digastric receives its nerve supply from the Anterior belly: mylohyoid nerve (CN V3); Posterior belly: facial nerve (CN VII).

Because a muscle can only contract when its nerve is intact, injury to the Anterior belly: mylohyoid nerve can weaken or paralyse the Digastric, impairing the movements it normally produces (elevates hyoid bone). This is why knowing the innervation is central to localising nerve lesions in clinical practice.

How to study the Digastric (the OIANS method)

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

Digastric quick facts

Region

Head & Neck

Group

Neck

Origin

Anterior belly: digastric fossa of mandible; Posterior belly: mastoid notch of temporal bone

Insertion

Intermediate tendon attached to body of hyoid bone (via fibrous sling)

Action

Elevates hyoid bone; depresses mandible (opens jaw)

Nerve

Anterior belly: mylohyoid nerve (CN V3); Posterior belly: facial nerve (CN VII)

Spinal roots

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Frequently asked questions

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