CorpusHuman Anatomy
MuscularMuscle

Digastric

Musculus digastricus

Also known as: digastricus, anterior belly of digastric, posterior belly of digastric

A suprahyoid muscle with two bellies joined by an intermediate tendon that is slung to the hyoid bone. Each belly has a different nerve supply.

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Overview

The posterior belly arises from the mastoid notch of the temporal bone. The anterior belly arises from the digastric fossa on the inner surface of the mandible near the midline. The two bellies meet at an intermediate tendon, held to the body and greater horn of the hyoid by a fibrous loop and perforating stylohyoid. With the lower border of the mandible, the digastric outlines the submandibular (digastric) triangle, which contains the submandibular gland. The two anterior bellies and the hyoid bound the submental triangle.

Because the two bellies come from different pharyngeal arches, they have different nerves: the anterior belly is supplied by V3 (nerve to mylohyoid; 1st arch) and the posterior belly by CN VII (2nd arch). The digastric depresses the mandible and elevates the hyoid. The posterior belly is a key surgical landmark ("the resident's friend"), because important structures lie deep to it: the carotid arteries, the internal jugular vein and CN X, XI and XII.

Parts & subdivisions

  1. Anterior belly
    Digastric fossa of the mandible → intermediate tendon. Supplied by the nerve to mylohyoid (V3).
  2. Posterior belly
    Mastoid notch → intermediate tendon. Supplied by the digastric branch of the facial nerve (VII).
  3. Intermediate tendon
    Attached to the hyoid by a fibrous sling.

Anatomy

Origin

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

Insertion

Intermediate tendon attached to the body and greater horn of the hyoid.

Action

Depresses the mandible against resistance; raises and steadies the hyoid.

Innervation

Anterior belly: nerve to mylohyoid (inferior alveolar branch of CN V3). Posterior belly: facial nerve (CN VII).

Nerve roots

CN V3 (anterior belly), CN VII (posterior belly)

Arterial supply

Anterior belly: submental artery (facial). Posterior belly: posterior auricular and occipital arteries.

Relations

The posterior belly crosses superficial to the internal and external carotid arteries, the internal jugular vein and the hypoglossal nerve.

Function

  • Depresses the mandible
  • Elevates (and steadies) the hyoid during swallowing and speech

Compiled from standard anatomy and physiology references — see the Muscular System sources. For education only; not medical advice.