In human anatomy, the masseter is one of the muscles of mastication. The masseter is a thick, somewhat quadrilateral muscle, consisting of two parts, superficial and deep. The fibers of the two portions are continuous at their insertion. The masseter muscle is sometimes the target of plastic jaw reduction surgery.

The medial pterygoid (or internal pterygoid muscle), is a thick, quadrilateral muscle of mastication. The mandibular branch of the fifth cranial nerve, the trigeminal nerve, innervates the medial pterygoid muscle. It consists of two heads. The bulk of the muscle arises as a deep head from just above the medial surface of the lateral pterygoid plate. The smaller, superficial head originates from the maxillary tuberosity and the pyramidal process of the palatine bone.

Temporalis is a broad, fan-shaped muscle on each side of the head that fills the temporal fossa, superior to the zygomatic arch so it covers much of the temporal bone. If the entire muscle contracts, the main action is to elevate the mandible, raising the lower jaw. Elevation of the mandible occurs during the closing of the jaws. If only the posterior part contracts, the muscle moves the lower jaw backward.