Digastricus

The digastricus, also known as the digastric muscle, is a paired muscle of the suprahyoid region. It consists of two muscular bellies, the anterior and the posterior, connected by an intermediate tendon that attaches to the body of the hyoid bone via a fibrous loop.

The anterior belly originates from the digastric fossa on the inner surface of the mandible and travels posteriorly to reach the intermediate tendon. The posterior belly arises from the mastoid notch and the medial aspect of the mastoid process of the temporal bone, then also inserts on the intermediate tendon. The intermediate tendon is anchored to the hyoid bone by a fibrous sling.

Innervation is compartmental: the anterior belly is supplied by the nerve to the mylohyoid, a branch of the mandibular division of the trigeminal nerve (V3). The posterior belly is supplied by the facial nerve (CN VII).

Functionally, the digastric muscles act to open the mouth by depressing the mandible when the hyoid is fixed, and to elevate the hyoid during swallowing and speech. They can stabilize the hyoid and help coordinate movements of the jaw and throat in complex mastication and deglutition.

Blood supply comes from separate sources for each belly: the anterior belly receives blood from the submental artery, a branch of the facial artery; the posterior belly is supplied by posterior branches of the stylomastoid, posterior auricular, or occipital arteries, depending on anatomical variation.

Clinical notes: the digastric forms part of the submental triangle and serves as a landmark in regional anatomy. Variations may include accessory digastric slips, and surgical or clinical procedures may exploit its anatomy for safety and access in the neck region.