Masseter

Origin: Zygomatic arch and maxilla

Insertion: Coronoid process and ramus of mandible

Artery: Masseteric artery

Nerve: Masseteric nerve (V3)

Action: Elevation (as in closing of the mouth) and protrusion of mandible

Antagonist: Platysma muscle

Description:
The Masseter is a thick, somewhat quadrilateral muscle, consisting of two portions, superficial and deep:

• The superficial portion, the larger, arises by a thick, tendinous aponeurosis from the zygomatic process of the maxilla, and from the anterior two-thirds of the lower border of the zygomatic arch; its fibers pass downward and backward, to be inserted into the angle and lower half of the lateral surface of the ramus of the mandible.
• The deep portion is much smaller, and more muscular in texture; it arises from the posterior third of the lower border and from the whole of the medial surface of the zygomatic arch; its fibers pass downward and forward, to be inserted into the upper half of the ramus and the lateral surface of the coronoid process of the mandible. The deep portion of the muscle is partly concealed, in front, by the superficial portion; behind, it is covered by the parotid gland. The fibers of the two portions are continuous at their insertion.