Temporal mandibular joint (TMJ)

Question 1

what forms the temporomandibular joint?

Answer 1

formed by the articulation of the mandible and the temporal bone of the cranium

Question 2

where is the TMJ located?

Answer 2

anteriorly to the tragus of the ear, on the lateral aspect of the face

Question 3

what does the TMJ consist of?

Answer 3

articulations between three surfaces:

the mandibular fossa and articular tubercle (from the squamous part of the temporal bone), and the head of mandible

Question 4

unique mechanism of TMJ?

Answer 4

the articular surfaces of the bones never come into contact with each other – they are separated by an articular disk

Question 5

significance of presence of articular disk?

Answer 5

The presence of such a disk splits the joint into two synovial joint cavities, each lined by a synovial membrane

Question 6

what covers the articular surface of the bones of TMJ?

Answer 6

covered by fibrocartilage, NOT hyaline cartilage

Question 7

how many ligaments are there to support to TMJ?

Answer 7

three extracapsular ligaments

Question 8

what are the 3 extracapsular ligaments stablising the TMJ?

Answer 8

Lateral ligament
Sphenomandibular ligament
Stylomandibular ligament

Question 9

where does the lateral ligament run?

Answer 9

from the beginning of the articular tubule to the mandibular neck

Question 10

what is the lateral ligament? function?

Answer 10

a thickening of the joint capsule, and acts to prevent posterior dislocation of the joint

Question 11

where does the sphenomandibular ligament originate and attach to?

Answer 11

Originates from the sphenoid spine (spine of sphenoid bone), and attaches to the mandible

Question 12

what is the stylomandibular ligmaent?

Answer 12

A thickening of the fascia of the parotid gland

Question 13

function of the stylomandibular ligament?

Answer 13

Along with the facial muscles, it supports the weight of the jaw

Question 14

what are movements of the TMJ produced by?

Answer 14

the muscles of mastication, and the hyoid muscles

Question 15

how do the 2 divisions of the TMJ differ?

Answer 15

have different functions:

1. Protrusion and Retraction
2. Elevation and Depression

Question 16

which part of the TMJ allows for protrusion and retraction?

Answer 16

The upper part of the joint allows protrusion and retraction of the mandible – the anterior and posterior movements of the jaw

Question 17

which muscle is responsible for protrusion of the TMJ?

Answer 17

The lateral pterygoid muscle

assisted by the medial pterygoid

Question 18

which muscle is responsible for retraction of the TMJ?

Answer 18

the geniohyoid and digastric muscles

Question 19

function of lower part of TMJ?

Answer 19

permits elevation and depression of the mandible; opening and closing the mouth

Question 20

what causes depression of the TMJ?

Answer 20

mostly caused by gravity

Question 21

if there is resistance against depression, which muscles assist depression of TMJ?

Answer 21

digastric, geniohyoid, and mylohyoid muscles

Question 22

what is elevation of TMJ caused by?

Answer 22

Elevation is very strong movement, caused by the contraction of the temporalis, masseter, and medial pterygoid muscles

Question 23

arterial supply to TMJ?

Answer 23

provided by the branches of the EXTERNAL carotid, principally the superficial temporal branch
(contributing branches: the deep auricular, ascending pharyngeal and maxillary arteries)

Question 24

what is the innervation to TMJ?

Answer 24

by the auriculotemporal and masseteric branches of the mandibular nerve (CN V3)

Question 25

what can cause dislocation of the TMJ?

Answer 25

can occur via a blow to the side of the face, yawning, or taking a large bite

Question 26

what happens in a dislocation of the TMJ?

Answer 26

The head of the mandible slips out of the manibular fossa, and is pulled anteriorly

Question 27

how do patients with TMJ dislocation present?

Answer 27

unable to close their mouth

Question 28

which nerves run close to TMJ?

Answer 28

The facial and auriculotemporal nerves run close to the joint, and can be damaged if the injury is traumatic

Question 29

how do posterior dislocations of TMJ occur?

Answer 29

possible, but very rare:
requiring a large amount of force to overcome the postglenoid tubercle (holds neck of mandible) and strong intrinsic lateral ligament

Question 30

what can arthritis of the TMJ cause?

Answer 30

can cause inflammation of the temporomandibular joint

Question 31

what do patients with arthritis of TMJ complain of?

Answer 31

jaw pain, stiffness and joint ‘grating’