• The temporalis muscle is a large, flat, and fan-shaped muscle. 
• It lies within the temporal fossa (a shallow depression on the lateral aspect of the skull) to the inferior temporal line of the lateral skull. 
• It arises from the entirety of the temporal fossa below the temporal line, as well as the deep surface of the temporal fascia.
• The temporalis muscle fibers converge inferiorly, forming a tendon that exists the temporal fossa passing underneath the zygomatic arch and inserting into the coronoid process of the mandible.

• It is the most powerful, strong, and quadrangular muscle of mastication. 
• It covers the lateral aspect of the ramus of the mandible and lies superficially to the pterygoids and temporalis, covering them. 
• It is composed of two layers.
• The superficial layer originates from the maxillary process of the zygomatic bone and the anterior two-thirds of the zygomatic arch and runs inferiorly and posteriorly to attach to the lateral surface of the angle and lower half of the ramus of the mandible. 
• The second, deep layer of the masseter muscle originates from the medial surface and inferior margin of the zygomatic arch and runs vertically downwards to insert onto the upper part of the ramus of the mandible and the coronoid process.

The nerve is supplied by the mandibular division of the Trigeminal Nerve. 

Blood is supplied by the masseteric artery, which emerges from the maxillary artery.

The major function of the masseter muscle is to elevate the mandible and approximate the teeth. The intermediate and deep muscle fibers are responsible for retracting the mandible and the function of the superficial fiber is to protrude the mandible. The deep fibers are important stabilizers of the TMJ.

• It is also a quadrangular muscle situated in the infratemporal fossa, located inferiorly to the lateral pterygoid.
• It originates on the pterygoid process, which is a downward-pointing process that extends from the sphenoid bone. 
• It is composed of two heads that have two sets of origins. 
• The larger deep head arises from the medial surface of the lateral pterygoid plate of the sphenoid bone and the adjacent pyramidal process of the palatine bone. 
• The smaller superficial head originates from the tuberosity of the maxilla. 
• The medial pterygoid muscle fibers converge inferiorly, forming a tendon that inserts on the medial ramus of the mandible posterior and inferior to the mylohyoid groove of the mandible.

The nerve is supplied by the medial pterygoid branch of the mandibular nerve.

Blood is supplied by the stems from the pterygoid branches of the maxillary artery.

• It is a triangular, short, and thick muscle situated in the infratemporal fossa. 
• It has horizontally orientated muscle fibers and two heads with two distinct origins. 
• The smaller, superior head arises from the inferior surface of the greater wing and infratemporal crest of the sphenoid bone, which forms the roof of the infratemporal fossa.
• The larger, inferior head originates from the lateral surface of the lateral pterygoid plate of the sphenoid bone. 
• The fibers from both heads merge and run posterolaterally to insert onto a shallow depression on the anterior aspect of the neck of the mandible called the pterygoid fovea.

The nerve is supplied by a branch of the anterior division of the mandibular nerve.

Blood is supplied by the pterygoid branch of 2nd part of the maxillary artery.

• Have shorter contraction times than most other body muscles.
• Incorporate more muscle spindles to monitor their activity
• Do not have Golgi tendon organs to monitor tension
• Do not get fatigued easily
• Psychological stress increases the activity of jaw-closing muscles
• Occlusal interferences cause a hypertonic synchronous muscle activity
• The closing movement is also determined by the height of the jaw