The posterior belly of the digastric is innervated by the facial nerve, reflecting its second branchial arch origin. It forms a key surgical landmark in the posterior triangle and parotid region, overlying the internal carotid artery, internal jugular vein, and the facial nerve trunk.
| Origin | Mastoid notch — medial to the mastoid process |
|---|---|
| Insertion | Intermediate tendon — anchored to the hyoid via a fibrous loop |
| Nerve Supply | Facial nerve — digastric branch (VII) |
| Blood Supply | Occipital and posterior auricular arteries |
| Actions | Elevates the hyoid during swallowing and speech; Depresses the mandible |
|---|
The posterior digastric belly is the critical landmark in parotidectomy — the facial nerve trunk exits the stylomastoid foramen and passes over the posterior belly. It also marks the boundary of the carotid sheath contents. In neck dissection, the posterior belly forms the superior boundary of level IIB nodal territory.
Palpated posterior to the submandibular gland as the diagonal muscle belly descending from the mastoid.
Identification of the posterior digastric belly as the inferior reference point for locating the facial nerve trunk at the stylomastoid foramen during superficial parotidectomy.
