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What joints form the TMJ?
- Hinge joint: for opening and closing- elevation and depression
- Gliding joint: protractions- anterior directions and retraction- posterior directions
What is the difference between the TMJ and other joints?
- 1. Fibrocartilage- to withstand heavy duty
- 2. Articular disc-compenstates for bone shape
- 3. Bilateral joint- both sides at same time
Is an attachment (shark fin- flat and pointy). The articulation of the mandible: smooth articulating surface.
- Thick, fibrous capsule that surrounds the joint
- Wraps superiorly around the articular eminence and fossa
- Wraps inferiorly around the neck and head of the condyle.
Articular joint disc
- Sometimes called meniscus
- Located between the temporal bone and condyle
- Attached to lateral and medial pole of condole
- Conforms to the shape of the adjacent articulating bones.
- Divides TMJ into two spaces- upper and lower synovial cavities
- Joint disc divides the synovial cavity into upper and lower joint cavities
- Synovial membrane (lining of cavities) secretes synovial fluid to: lubricate cavity, nutritive functions for articular cartilage, and is a shock absorber.
Supporting soft tissues: TMG ligaments
- 1) TMJ ligament- located on lateral side of joint; reinforces joint capsule; runs from zygomatic arch (anterior to joint capsule) and inserts into posterior surface of rams below condyle; prevents excessive retraction (backwards movement)
- 2) Sphenomandibular ligament- located on the medial side of the mandible; runs from spine of sphenoid to lingua of mandible near mandible foramen; during protrusion (forward movement), ligament becomes taut.
- 3) Stylomandibular ligament- located on the posterior aspects of the mandible; runs from styloid process to angle of mandible; during protrusion (forward movement), ligament becomes taut.