masticationmasseter

The masseter is a thick, rectangular muscle of the face that plays a central role in mastication (chewing). It is one of the primary muscles of mastication, along with the temporalis, medial pterygoid, and lateral pterygoid. The masseter is among the strongest jaw muscles relative to its size and is primarily responsible for elevating the mandible to close the mouth.

Anatomically, the masseter has two heads: a superficial head and a deep head. The superficial head originates from the inferior border of the zygomatic arch and inserts on the lateral surface of the mandible near the angle. The deep head arises from the inner surface of the zygomatic arch and inserts higher on the ramus of the mandible. Both heads lie in the cheek region, with the muscle extending from the cheekbone to the mandible.

Innervation is by the mandibular division of the trigeminal nerve (CN V3), via the masseteric nerve. The blood supply comes from the masseteric artery, a branch of the maxillary artery.

Functionally, the masseter elevates the mandible to close the mouth and can contribute to protraction or retrusion depending on fiber activation. Unilateral contraction aids in grinding and side-to-side movement of the jaw when coordinated with other masticatory muscles.

Clinical notes include masseter muscle hypertrophy, which can occur with bruxism or intensive chewing and may present as facial contour changes. The muscle is also considered in the assessment of temporomandibular disorders and in certain surgical or dental procedures involving the jaw and cheek region.