The masseter is a paired, thick and strong quadrangular-shaped masticatory muscle that elevates the lower jaw. Together with the temporal, lateral and medial pterygoid muscles, it is classified as the primary muscle of mastication.

The masseter is located in the cheeks, extending between the zygomatic arch, the angle of the mandible and the lateral surface of the mandibular ramus. This muscle is composed of several parts, and they are as follows:

Superficial part
Deep part
Coronoid part

Each part has a different origin and insertion sites. The superficial part of the muscle is covered with the masseteric (parotideomasseteric) fascia. The masseter acts at the temporomandibular joint (TMJ), providing the elevation and protrusion of the mandible.

Origin: superficial part - temporal process of the zygomatic bone and inferior border (anterior two-thirds) of the zygomatic arch; deep part - entire inferior aspect of the zygomatic arch; coronoid part - medial surface of the zygomatic process of the temporal bone and deep layer of the deep temporal fascia.

Insertion: superficial part - masseteric tuberosity at the angle of the mandible and inferior aspect of the lateral surface of the mandibular ramus; deep part - ramus of the mandible superior to the insertion site of the superficial part; coronoid part - base and posterior margin of the coronoid process of the mandible.

Action: elevation of the mandible, protrusion of the mandible (superior anterior fibers); muscle also aids in stabilization of the mandible.

Innervation: masseteric nerve that is a branch of the mandibular division (CN V3) of the trigeminal nerve (CN V).

Blood supply: masseteric artery that is a branch of the maxillary artery.

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Masseter muscle