Quick Facts
Origin: Mastoid notch of temporal bone.
Insertion: Intermediate tendon of digastric muscle.
Action: Depresses mandible; elevates hyoid bone.
Innervation: Digastric branch of facial nerve (CN VII).
Arterial Supply: Posterior auricular and occipital arteries.
Origin
The posterior belly originates from the mastoid notch, which is found along the internal surface of the mastoid process of temporal bone.
Insertion
Both the anterior and posterior bellies of the digastric muscle insert into the intermediate tendon of digastric muscle. This tendon pierces the stylohyoid muscle and then passes through a fibrous sling that is attached to the hyoid bone.
The fibers of the posterior belly descend anteriorly before attaching to the intermediate tendon.
Key Features & Anatomical Relations
The platysma, sternocleidomastoid, stylohyoid, and longissimus capitis muscles, as well as the mastoid process of the temporal bone, sit superficial to the digastric muscle.
The fact that the anterior and posterior bellies have separate innervation reflects their embryological origins. The anterior belly is derived from the first pharyngeal arch and, thus, is innervated by the trigeminal nerve (CN V). The posterior belly of the digastric muscle is derived from the second pharyngeal arch and, therefore, it is innervated by the facial nerve (CN VII).
Actions
Overall, the digastric muscle is involved in multiple actions:
- depresses the mandible at the temporomandibular joint;
- elevates the hyoid bone (Standring, 2016).
References
Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41st edn.: Elsevier Limited.
