Temporal mandibular joint (TMJ)

Question 1

What is it?

Answer 1

joint formed between the condyle of the mandibular + temporal bone at the base of the skull

Question 2

When the mouth is closed

Answer 2

the condyle rests in a hollow region of the temporal bone called the glenoid fossa

Question 3

The front edge of the glenoid fossa

Answer 3

is formed into a ridge called articular eminence

Question 4

Between these two surfaces

Answer 4

there is a disc of fibrous tissue called the meniscus, which prevents the two bones from grating against each other

Question 5

During the first stage

Answer 5

of the mouth opening, the condyle remains in the glenoid fossa

Question 6

As the mouth opens further

Answer 6

the condyle slides down + forwards from the glenoid fossa along the slope of the articular eminence

Question 7

When condyle reaches

Answer 7

the crest of articular eminence, the mouth is open to its fullest + the incisors can grasp food between their cutting edges

Question 8

When closing

Answer 8

the glenoid fossa goes back to its original position, produces shearing action of incisors thereby cutting food into smaller pieces for chewing

Question 9

Dislocation of the jaw

Answer 9

occurs when the condyle slips too far forward + gets stuck infront of the articular eminence
it is treated by pressing down on the molars to force the condyle down + back

Question 10

When the meniscus slips

Answer 10

in front or behind its normal position during opening + closing, the pt experiences ‘jaw clicking’. this disarrangement of the joint Is called subluxation

Question 11

Gliding movement

Answer 11

mainly occurs when the disc + the condyle together slide up + down the articular eminence, allowing mandible to move forwards + backwards

Question 12

Rotational movement

Answer 12

occurs when the condyle rotates anteriorly + posteriorly over the surface pf the disc itself, which remains static, allowing the mandible to move down + up

Question 13

Lateral movement

Answer 13

occurs when one joint glides alone, so that the other condyle rotates sideways over its disc, swinging the mandible on the side opposite from the gliding action

Question 14

Chewing

Answer 14

is brought about by rotational movements of the mandible which swings from side to side, crushing food between the cusps of opposing molars + premolars

Question 15

The opening movements of the mandible

Answer 15

are due to actions of the suprahyoid muscles which lie in floor of mouth + in throat. the closing + chewing action are due to actions of muscles of mastication which run between the mandible + cranium or facial bones