Muscles of Mastication

Temporalis

Broad fan shaped muscle *O:* Temporal fossa *I:* Coronoid process and anterior ramus of the mandible. *A:* whole muscle contracts= elevation of mandible Posterior fibers contracted= retrusion (backwards motion)

Masseter

most superficial and strongest muscles that has both superficial and deep head at differing depths. *Deep O:* Zygomatic arch and zygoma *Deep I:* lateral surface of the angle of the mandible *Superficial O:* Zygomatic arch and zygoma *Superficial I:* lateral surface of the angle of the mandible *A:* Raises (elevates) mandible *Clench teeth, you can feel the muscle thru cheek*

Muscles of mastication (4 paired muscles)

1. masseter muscle 2. temporalis muscle 3. medial pterygoid muscle 4. lateral pterygoid muscle * all are innervated by the fifth cranial nerve*

Medial pterygoid muscle

Has superficial and deep heads located at differing depths. *Deep head O:* Lateral pterygoid plate of spenoid bone *Deep head I:* ramus and angle of mandible *Superficial head O:* Palatine bone and maxillary tuberosity *Superficial head I:* ramus and angle of mandible *A:* raises (elevates) the lower jaw (like masseter muscle but weaker)

Lateral pterygoid muscle

Short thick muscle superior or inferior head depending on the location. *Superior head O: *greater wing of sphenoid bone *Superior head I:* mandibular condyle inner surface *Inferior head O:* lateral pterygoid plate of sphenoid bone *Inferior head I:* TMJ disc and capsule *A:* Opening (depressing) the jaw and protruding mandible when both right and left sides contact. *Only muscle of mastication that depresses (lowers) the jaw.*