Head and neck muscles (chewing, facial, and throat muscles)

Anterior belly of digastric

Musculus digastricus, venter anterior

Origin

Digastric fossa on the inner surface of the mandible, near the symphysis menti

Insertion

Connected to the posterior belly via the intermediate tendon (anchored by a fibrous sling to the hyoid bone)

Function

Opens the mouth (depresses the mandible) when the hyoid bone is fixed; elevates the hyoid bone during swallowing when the mandible is fixed

Innervation

Mylohyoid nerve (branch of the inferior alveolar nerve, CN V3)

Movement & chain

Works together with mylohyoid and geniohyoid in the suprahyoid group: during swallowing these muscles pull the hyoid-larynx complex up and forward, while with the hyoid fixed (by the infrahyoid muscles) they instead assist mouth opening.

Palpation

Felt as a taut band under the chin, medial to the lower border of the mandible, during resisted mouth opening.

Clinical

Landmark in submental/submandibular surgery and in assessment of the floor of the mouth; dysfunction can contribute to swallowing problems (dysphagia).

Segmental innervation

CN V3 (mylohyoid branch), motor.

In clinical practice

Together with the mandible and hyoid bone forms the boundaries of the submandibular triangle, an important landmark for palpating submandibular glands and lymph nodes.

Region in the model

Head and neck muscles (chewing, facial, and throat muscles)