TMJ and Muscles of Mastication

Bones

Bones

- temporal bone
- sphenoid bone
- zygomatic bone
- maxilla
- mandible

Parts of the Mandible

- condylar/condyloid process
- neck
- mandibular notch
- coronoid process (anterior)
- ramus
- angle
- body

Temporal bone

- mastoid process
- styloid process
- mandibular fossa (where condylar process sits)
- articular tubercle/eminence (limits anterior movement of mandible when jar is lowered)

TMJ

- synovial joint
- upper and lower compartments separated by articular disc
- upper: gliding (protrusion and retraction, side to side)
- lower: rotation (elevation and depression)

TMJ ligaments

- lateral temporalmandibular ligament: attaches to zygomatic arch and posterior portion of neck of mandible (limits posterior movement of mandible)
- stylomandibular ligament: ramus to styloid process (limits anterior protrusion)
- sphenomandibular ligmament: ramus to sphenoid bone (pivot)

Lateral Pterygoid muscle

- superior head: attaches to root of infratemporal fossa and lateral portion of lateral pterygoid plate
- inferior head: attaches to lateral portion of lateral pterygoid plate
- both move posteriorly and fuse and attach to condylar process of mandible
- act bilaterally: protrude jaw (opening)
- unilateral: swings jaw to contralateral side

Medial Pterygoid Muscle

- deep head: attached to medial aspect of lateral pyerygoid plate
- superficial head: attached to maxilla and palatine bones
- both fuse posterio-internally and inserts onto ramus of mandible
- act bilaterally: close jaw, assist in protrusion
- unilateral: swing jaw to contralateral side (grinding motion)

Temporalis muscle

- arises from temporal fossa
- fibers attach to coronoid process on mandible and ramus of mandible
- anterior fibers run vertically (assist in closing jaw)
- posterior horizontal fibers (retract mandible)

Masseter muscle

- two heads
- originates from zygomatic bone and zygomatic arch
- attaches to ramus and angle of the mandible
- elevates mandible and retracts