Masseter Muscle: Parts ,Origin and insertion
The masseter muscle consists of a superficial and a deep part. The origin of the superficial part is on the zygomatic arch and its insertion is on the lateral masseteric tuberosity at the angle of the mandible. The deep part also arises on the zygomatic arch but inserts on the lateral surface of the ascending ramus. Portions of the deep part also insert on the joint capsule and the disk (Frommer and Monroe 1966, Meyenberg et al. 1986, Dauber 1987). In this way the masseter can influence the capsule receptors by changing the capsule tension.
Pars superficialis of the masseter muscle
Left: Schematic drawing of the pars superficialis. The masseter has a higher concentration of capillaries relative to the diameter of the fibers than all the other skeletal muscles (Staletal. 1996).
Right: Macroscopic anatomical preparation of the masseter muscle. The resultant force of the pars superficialis is in an anterosuperior direction. The posterior part of the pars superficialis is composed of up to 45% type-IIB fibers (Eriksson and Thornell 1983), which have a high threshold and are fatigue-resistant.
Left: Schematic drawing.
Right: The pars profunda revealed in an anatomical dissection. The muscle has a relatively broad insertion on the zygomatic arch from which it pulls on the lateral surface of the ascending ramus of the mandible. The posterior part of the pars profunda also inserts into the lateral third of the disk-capsule complex (Merida Velasco et al. 1993, Bade et al. 1994). Only approximately 25% of the muscle fibers of the pars profunda are of type IIB.
Origin and insertion of the masseter muscle
Schematic drawing showing the areas of origin and insertion of the masseter muscle. The origin of the pars superficialis is on the inferior surface of the zygomatic arch anterior to that of the pars profunda. The insertion of the pars superficialis lies on the lateral surface of the angle of the mandible. At the inferior border of the mandible it is continuous with the medial pterygoid muscle on the inner surface of the mandible. The pars profunda inserts above the masseteric tuberosity on the ascending ramus of the mandible.