Temperomandibular Joint

Question 1

What type of joint is the TMJ?

Answer 1

Synovial hinge-type joint

Question 2

What nerve innervates the TMJ?

Answer 2

Auricotemporal nerve - branch of CNVc

Question 3

What is the anatomy of the TMJ?

Answer 3

Articular surfaces lined with fibrocartilage

Seperated by fibrocartilaginous disc

Stabilised by joint capsule and ligaments

Question 4

How does the jaw open?

Answer 4

Initial opening = hinge action by inferior half of the joint cavity

Question 5

How do you open the jaw widely?

Answer 5

Wider opening = condyle glides over articular tubercle - movement occurs in superior half of joint

Question 6

How does the jaw retract/protract?

Answer 6

Gliding movements at superior joint capsule

Question 7

What muscles are involved in elevation of the mandible?

Answer 7

Masseter
Temporalis
Medial pterygoid

Question 8

What muscles are involved in protrusion of the mandible

Answer 8

Lateral pterygoid

Medial pterygoid

Question 9

What muscles are involved in retraction of the mandible?

Answer 9

Posterior fibres of temporalis

Question 10

What can cause TMJ dislocation?

Answer 10

Facial trauma

Yawning

Question 11

What happens in TMJ dislocation?

Answer 11

Jaw locks in open position due to anterior dislocation of condyle over anterior tubercle

Muscles contract to keep joint locked in anterior displacement