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What type of joint is TMJ
- Modified codyloid:
- has condyle
- has fossa
- can move on two axis, plus some extra movement (modified)
- loose capsule --> more mobile
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TMJ Capsule
Runs from temporal bone to neck of mandible
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Anterior and posterior tuburcles
Prevent too much movement forward and backwards
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Type of cartilage over articular surface
fibrocartilage (different than most joints (usually hyalin)) --> stronger joint
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Sphenomandibular ligament
- Attachments: medial surface of ramus up to spine of sphenoid
- Functions: checks angle of mandible so it doesn't move too much - allows jaw to rotate instead of dropping down and forward; suspends mandible
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Stylomandibular ligament
- Attachments: styloid process down to angle of mandible
- Functions: guides mandible;
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Temporomandibular/lateral ligament
- Attachments: temporal bone down to neck of mandible
- Thickening of joint capsule
- Functions: prevents excessive lateral excursion and posterior displacement (along with posterior tubercle)
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Articular Disc
- fibrocartilage
- lacks blood supply
- allows jaw to move more freely
- attachment for lateral pterygoids
- with full opening of jaw, lateral excursion, protrusion and retrusion: articular disc drops down out of fossa
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Masseter
- Origin: Anterior and posterior zygomatic arch
- Insertion: Angle and lateral ramus of mandible
- Innervation: CN V3
- Main Action: Elevates and protrudes mandible; deep fibers retrude mandible
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Temporalis
- Origin: Temporal fossa
- Insertion: Ramus of mandible and coronoid process
- Innervation: CN V3
- Main Actions: Elevates mandible; posterior fibers retrude mandible
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Lateral Pterygoid
- Origin: Greater wing of sphenoid, lateral pterygoid plate
- Insertion: neck of mandible, articular disc, and capsule of TMJ
- Innervation: CN V3
- Main Actions: Acting together, protrude mandible and depress chin; acting alone and alternately, produces side-to-side movements
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Medial Pterygoid
- Origin: Medial surface of lateral pterygoid plate
- Insertion: Medial surface of mandible near angle
- Innervation: CN V3
- Main Actions: Elevates mandible; acting together, protrude mandible; acting alone, protrudes side of jaw; acting alternately, produces grinding motion
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Muscles that open jaw
- digastric
- lateral pterygoid
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Muscles the close jaw
- masseter
- temporalis
- medial pterygoid
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Muscles of lateral excursion
- same side:
- temporalis
- opposite side:
- medial pterygoid
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