The posterior belly, longer than the anterior belly, arises from the mastoid notch which is on the inferior surface of the skull, medial to the mastoid process of the temporal bone. Likewise, we speak of the digastric even though there is a right and left digastric muscle. For example, we speak of the deltoid, even though there is one deltoid in each shoulder. In most anatomical discussions, the singular is used to refer to a muscle, even when each person actually has two of that muscle - one on the right side, and another on the left. The two bellies of the digastric muscle have different embryological origins, and are supplied by different cranial nerves.Įach person has a right and left digastric muscle. The digastricus (digastric muscle) consists of two muscular bellies united by an intermediate rounded tendon. Opens the jaw when the masseter and the temporalis are relaxed. If the hyoid is being held in place (by the infrahyoid muscles), it will tend to depress the mandible (open the mouth). When the digastric muscle contracts, it acts to elevate the hyoid bone.
Īnterior belly - digastric fossa (mandible) posterior belly - mastoid process of temporal boneĪnterior belly - mandibular division (V3) of the trigeminal (CN V) via the mylohyoid nerve posterior belly - facial nerve (CN VII)Īnterior belly - Submental branch of facial artery posterior belly - occipital artery It belongs to the suprahyoid muscles group.Ī broad aponeurotic layer is given off from the tendon of the digastricus on either side, to be attached to the body and greater cornu of the hyoid bone this is termed the suprahyoid aponeurosis.
It lies below the body of the mandible, and extends, in a curved form, from the mastoid process to the symphysis menti.
However, other muscles that have two separate muscle bellies include the ligament of Treitz, omohyoid, occipitofrontalis. The term "digastric muscle" refers to this specific muscle. The digastric muscle (also digastricus) (named digastric as it has two 'bellies') is a small muscle located under the jaw.
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