Digastric Muscles Under the Skin

Description

Centered in the anterior neck, the paired digastric muscles run from the mandible to the hyoid apparatus as two bellies joined by an intermediate tendon that is tethered to the hyoid bone by a fibrous sling. The anterior belly lies inferior to the mandibular body near the digastric fossa and sits superficial to the mylohyoid, while the posterior belly courses posteroinferiorly toward the mastoid region, passing deep to the submandibular area and anterior to the upper sternocleidomastoid. Nearby relationships commonly included in an under-the-skin head and neck rendering include the masseter on the lateral mandibular ramus, the temporalis over the temporal fossa, the mandibular dentition, and the upper cervical vertebrae aligned posterior to the pharyngeal airway. Small but important. Functionally, the digastric is a key suprahyoid muscle for jaw opening and hyoid elevation, and its anatomy is routinely tested because the intermediate tendon and paired bellies create reliable surface and deep landmarks in the submandibular region. Surgeons use the digastric as a reference during submandibular gland excision, level I neck dissection, and exposure of the hypoglossal nerve (CN XII), which typically runs deep to the posterior belly before crossing the hyoglossus. Variation is common, including accessory anterior bellies or asymmetry, which can mimic a submental mass on ultrasound or complicate interpretation of cross-sectional imaging of the floor of mouth. Use this asset in gross anatomy and head and neck modules to teach suprahyoid compartment anatomy, in surgical atlases discussing the submandibular triangle and cervical lymph node levels, or in radiology primers correlating the digastric with CT and MR landmarks around the hyoid and mandible. Anatomical accuracy verified by SciePro's Medical Advisory Board.