masseterlihase

The masseter muscle, known in Estonian as masseterlihase, is a paired facial muscle of mastication. It is one of the primary muscles responsible for elevating the mandible to close the mouth and plays a central role in chewing. The muscle has two parts, the superficial head and the deep head.

The superficial head originates from the inferior border and anterior two-thirds of the zygomatic arch and inserts along the lower border and angle of the mandible. The deep head originates from the inner surface of the zygomatic arch and inserts on the upper part of the ramus of the mandible. The masseter lies in the cheek region, superficial to the mandible, and is covered by the masseteric fascia; it is situated anterior to the parotid gland.

Innervation is provided by the masseteric nerve, a branch of the mandibular division (V3) of the trigeminal nerve. The primary arterial supply comes from the masseteric arteries, branches of the maxillary artery, with venous drainage through the pterygoid venous plexus to the maxillary vein.

Functionally, the masseter’s main action is the elevation of the mandible to close the jaw. It also contributes to jaw protrusion and, to a lesser extent, to lateral (side-to-side) movements during chewing.

Clinical notes: Masseter hypertrophy can occur with bruxism or heavy chewing and may influence facial contour. In some contexts, botulinum toxin injections are used to reduce overactivity for therapeutic or cosmetic purposes.