Tmj Flashcards
What kind of joint is tmj
Ginglymoarthodial joint (gliding + hinge motion) Synovial joint Bilateral diarthrosis
What are the functions of articular disc
Stabilise TMJ. Make articular surface congruent. Reduce wear of tmj. Aid in lubrication of tmj. Divide joint into upper and lower compartment for translation and hinge motion respectively
What are the 4 ligaments of tmj, state their attachments
Lateral (temperomandibular): articular tubercle on zygomatic process, extend downwards and backwards to attach to lateral posterior border of condyle neck. Prevent posterior displacement of resting condyle (origin anterior to insertion)
Sphenomandibular: sphenoid spine to lingula above mylohyoid groove
Stylomandibular ligament: styloid process apex to angle of mandible (posterior border). Limit mandibular movement.
Collateral ligament/capsule: 2 bundles of symmetrical fibres that originate at intermediate fascia of articular disc and insert at medial and lateral poles of condyle. Stabilise tmj
What is the neurovascular supply of tmj
Maxillary artery and superficial temporal artery
Masseteric and auriculotemporal branch of CN V3
What are some the blood vessels related to tmj
Maxillary artery inferiorly. Middle meningeal artery anteriorly (from maxillary artery, going into middle cranial fossa via spinosum to supply dura mater). Superficial temporal artery posteriorly
4 histological layers of articular disc
Articular zone: Dense fibrous connective tissue, poor blood supply, better ability to repair, good adaptation to sliding movement, shock absorber, less susceptible to aging and breakdown Proliferative zone (undifferentiated mesenchymal cells): mainly cellular, undifferentiated mesenchymal cells, proliferation and regeneration for life Cartilaginous zone: fibrocartilage in random orientation to from 3D network, to resist compressive and lateral forces. Becomes thinner with age due to lateral forces Calcified zone: chondrocytes, chondroblasts, osteoblasts
APCC
Describe articular layer of articular disc
Poor blood supply. Dense fibrous connective tissue. Shock absorber. Better ability to repair
How many mm of mouth opening before translational movement sets in
20-25mm
What muscles depress mandible
Lateral pterygoid, geniohyoid, mylohyoid, digastric
What muscles elevate mandible
Medial pterygoid, temporalis, masseter
What muscles cause protrusion of mandible
Medial and lateral pterygoid,
What muscles cause retraction of mandible
Posterior fibres of temporalis
How does tmj change with age
Synovial folds and villi increase and become more fibrotic. Less synovial fluid. Decreased lubrication
Osteoporosis of underlying bone and thinning of condyle cartilaginous zone leads to tmj dysfunction
Hyalinisation and chondroid (cartilage) changes lead to decrease extensibility of disc and capsule
Decreased nerves in disc and capsule
What is eccentric jaw opening
Preparation for power stroke of mastication. Condyle on non working side slide back and forth during lateral movement. Mainly condylar translation in forward and downward direction.
What does reduction mean
Articular disc able to recapture normal relationship with condyle upon opening
