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Muscles of Mastication
Muscles of mastication are involved in chewing.
- Originates on the temporal fossa of the temporal bone and inserts on the coronoid process and anterior ramus of the mandible; it elevates and retracts the mandible.
- Originates on the zygomatic bone and arch and inserts on the angle and lateral ramus of the mandible, which it elevates.
Medial pterygoid has two heads:
- The deep head originates on the medial aspect of the lateral pterygoid process of the sphenoid and inserts on the medial surface of the angle and ramus of the mandible.
- The superficial head originates on the tuberosity of the maxilla and inserts with the deep head on the mandibular angle.
- The medial pterygoid elevates the mandible and moves it laterally.
The lateral pterygoid also has two heads:
- The upper head originates from the infratemporal fossa of the sphenoid and inserts on the temporomandibular joint capsule and mandible.
- The lower head originates from the lateral surface of the lateral pterygoid plate and inserts with the upper head.
- The lateral pterygoid protrudes the mandible and moves it laterally.
Movements of the mandible at the temporomandibular joint:
- Protrusion moves the mandible anteriorly; the lateral pterygoid muscles produce this movement.
- Retraction moves the mandible posteriorly; the masseter produces this movement.
- Elevation moves the mandible superiorly towards the upper teeth; temporalis, masseter, and the medial pterygoid produce this movement.
- Depression moves the mandible inferiorly.