Anterior belly of digastric muscle

At a glance

English

Anterior belly of digastric muscle

Latin (TA2)

Venter anterior musculi digastrici

System

Muscle

Region

Neck

Side

Paired, left and right

About the anterior belly of digastric muscle

The digastric is a small muscle below the jaw made of two fleshy bellies joined end to end by a round tendon. The anterior belly is the shorter front half. It lies just under the skin and platysma beneath the chin, resting on the outer surface of mylohyoid, and it is one of the suprahyoid muscles that connect the hyoid bone to the skull and mandible.

It arises from the digastric fossa, a shallow pit just inside the mandible's lower edge beside the midline. From there it runs backwards and downwards to the intermediate tendon. That tendon passes through the stylohyoid muscle and is held to the body and greater horn of the hyoid by a fibrous sling, sometimes lined with a synovial sheath; this sling lets the muscle act like a rope over a pulley. The posterior belly continues from the tendon back to the skull.

The two bellies come from different pharyngeal arches. The anterior belly develops from the first arch, like the chewing muscles, and so is supplied by the nerve to mylohyoid, which leaves the inferior alveolar nerve, itself from the trigeminal's mandibular division. Its blood comes mainly from the submental branch of the facial artery. When the hyoid is held still by the infrahyoid muscles, it pulls the chin down and back to open the mouth; when the jaw is fixed, it lifts the hyoid forwards, which helps in swallowing, speech and chewing.

The paired anterior bellies frame the submental triangle, a small midline space between them above the hyoid that contains lymph nodes draining the chin and lower lip. Each belly also forms the front edge of the submandibular triangle. Variations are common: this belly may be doubled, send slips to the jaw or to mylohyoid, cross to join the opposite side, or be missing altogether.

Attachments, action and supply

Origin

Digastric fossa, inside the mandible's lower edge near the midline.

Insertion

Intermediate tendon, held to the body and greater horn of the hyoid by a fibrous sling.

Action

Depresses and retracts the mandible when the hyoid is fixed; raises the hyoid when the jaw is fixed.

Nerve supply

Nerve to mylohyoid, off the inferior alveolar nerve (trigeminal, CN V3).

Blood supply

Submental branch of the facial artery.