Lec 6 - Temporomandibular Joint

Question 1

What is the temporomandibular joint?

Answer 1

It is the articulation between temporal bone and mandible.

Question 2

What kind of joint is the temporomandibular joint?

Answer 2

It is a synovial hinge-type joint divided into two synovial cavities by fibrocartilaginous disc.

Question 3

What innervates the auriculotemporal nerve?

Answer 3

It is innervated by a branch of the mandibular division of trigeminal nerve (Vc).

Question 4

What conditions involve the temporomandibular joint?

Answer 4

1. TMJ disorder —> there may be pain particularly at the ear, jaw, lateral side of the head, clicking and locking.
2. TMJ dislocation —> this is secondary to facial trauma and may be due to yawning.
3. Arthritis.

Question 5

Describe the anatomy of the temporomandibular joint?

Answer 5

• It has articular surfaces of bones which are lined with fibrocartilage and do not come into direct contact.
• It is separated by fibrocartilaginous disc.
• The TMJ divides the joint into two synovial-line cavities filled with synovial fluid.
• The TMJ is stabilised by a joint capsule and a series of 3 extracapsular ligaments

Question 6

What movements happen at the TMJ?

Answer 6

1. initial opening of jaw (depression of the mandible) is by hinge (rotational) action in the inferior half of the joint cavity.
2. Opening the jaw more widely requires the mandibular condyle to glide forward over the articular tubercle –> this movement occurs in the superior half of the joint cavity.
3. Simple retraction and protraction of the mandible involves movements at the superior joint capsule (gliding)

Question 7

Which muscles are involved in the elevation of the mandible at the TMJ?

Answer 7

1. masseter
2. temporalis
3. medial pterygoid

Question 8

Which muscles are involved in the depression of the mandible at the TMJ?

Answer 8

1. lateral pterygoid.
2. The following muscles work against resistance:
   - –> platysma
   - –> suprahyoids

Question 9

Which muscles are involved in the protrusion/ protraction of the mandible at the TMJ?

Answer 9

1. lateral pterygoid
2. medial pterygoid assists it.
3. anterior fibres of the temporals also assist.

Question 10

Which muscles are involved in the retraction of the mandible at the TMJ?

Answer 10

done by the posterior fibres of the temporals which inserts into the coronoid process.

Question 11

Which muscles are involved in the grinding (lateral and rotational movement) of the mandible at the TMJ?

Answer 11

done by the muscles of two sides working co-operatively.

—> these are the lateral pterygoids which laterally deviate the mandible.

Question 12

What can cause dislocation of the TMJ?

Answer 12

1. facial trauma —> blow to side of Jaw especially when it is open.
2. yawning.

Question 13

what happens during the dislocation of the TMJ?

Answer 13

• jaw locks as joint fixes in open position due to anterior dislocation of condyle over the articular tubercle, which lies anterior to the tubercle.
• contraction of the muscles around the joint (muscles of mastication) keep the joint locked in anterior displacement.