The digastric muscle (also known as digastric, latin: musculus digastricus) is one of the suprahyoid muscles of the neck, which lies below the mandible. The digastric muscle is composed of two muscular bellies, the anterior and posterior bellies, that are connected by an intermediate tendon. Each belly of the digastric muscle has a different embryological origin, and that is why they do not have a common nerve supply.
The digastric muscle has an intermediate tendon which acts on the lesser horn of the hyoid bone by means of a connective tissue band. The posterior belly of the digastric muscle passes from the temporal bone to the intermediate tendon, while the anterior belly extends from the mandible to the intermediate tendon. To be more precise, the origin site of the anterior belly of the digastric muscle is the digastric fossa of the mandible, but the posterior belly originates from the mastoid notch of the temporal bone. Both bellies of the digastric muscle insert into the intermediate tendon attached to the hyoid bone.
The digastric muscle opens the jaw when the masseter and the temporalis are relaxed.
The nerve supply for the digastric muscle is provided by two cranial nerves. The digastric branch of the facial nerve (CN VII) innervates the posterior belly, while the mylohyoid nerve, a branch of the mandibular nerve (CN V3) supplies the anterior belly of the digastric muscle.