Jaw muscles

Question 1

What kind of joint is the temporomandibular joint?

Answer 1

Modified synovial hinge joint

Question 2

What movements does the temporomandibular joint permit?

Answer 2

1) Gliding
2) Rotation
3) Flexion (elevation)
4) Extension (depression)

Question 3

The temporomandibular joint is formed by articulations between what?

Answer 3

Articulations between the mandibular fossa and articular tubercle of the temporal bone and the condylar process of the mandible

Question 4

What is the articular disc and what does it do in the temporomandibular joint?

Answer 4

Separates the 2 articulating surfaces of the TMJ

Creates a superior and inferior articular cavity

Question 5

The joint capsule of the TMJ is thickened laterally by what and what does this serve to do?

Answer 5

Thickened laterally by the lateral ligament of the TMJ which serves to strengthen the joint

Question 6

Which bony structure acts with the lateral ligament to prevent dislocation of the TMJ?

Answer 6

Mastoid process

Question 7

Other than the lateral ligament of the TMJ what 2 other ligaments support the joint and what are their attachments?

Answer 7

1) Sphenomandibular ligament - lies medial to the TMJ from spine of the sphenoid bone at base of the skill to the lingula (slight bony protrusion) on medial side of ramus of the mandible
2) Stylomandibular ligament - passes from the styloid process of the temporal bone to the posterior margin of the angle of mandible

Question 8

What must happen in the TMJ in order for the mouth to open?

Answer 8

The condylar process of the mandible must glide anteriorly to lie directly beneath the articular tubercle - protrusion.

Question 9

Depression of the mandible (opening the mouth) is only possible when what?

Answer 9

When the mandibular condyle is fuller protracted beneath the articular tubercle)

Question 10

Which movement is essential to grind food between the molars?

Answer 10

Protrusion of the condylar process and depression of the mandible unilaterally
As the contralateral condylar process will undergo rotation on the inferior surface of the articular disc and grinding movements will occur

Question 11

What force is usually sufficient for depression of the mandible?

Answer 11

Gravity

Question 12

Which muscle contributes to depression of the mandible or opening of the mouth against resistance?

Answer 12

Lateral pterygoid and hyoid muscles

Question 13

What are the 4 principle muscles of mastication?

Answer 13

1) Masseter
2) Temporalis
3) Medial pterygoid
4) Lateral pterygoid

Question 14

Elevation of the mandible requires the action of what 3 muscles of mastication?

Answer 14

1) Masseter
2) Temporalis
3) Medial pterygoid

Question 15

Depression of the mandible requires the action of which 2 muscles?

Answer 15

1) Lateral pterygoid

2) Hyoid muscles

Question 16

Protrusion of the mandible requires the action of which muscle of mastication?

Answer 16

Lateral pterygoid

Question 17

Retrusion/retraction of the mandible requires the action of which muscle of mastication?

Answer 17

Temporalis

Question 18

Lateral movements of the mandible require the actions of which 2 muscles of mastication?

Answer 18

1) Medial pterygoid

2) Lateral pterygoid

Question 19

What is the nerve supply to the muscles of mastication?

Answer 19

V3 - mandibular nerve
Masseter - masseteric nerve from anterior trunk of V3
Medial and lateral pterygoid - nerve to the medial and lateral pterygoid from V3
Temporalis - Deep temporal nerve from the anterior trunk of V3

Question 20

What foramina does the mandibular nerve (CN V3) pass through?

Answer 20

Foramen ovale

Question 21

Unilateral damage to the CN V3 leads to jaw deviation to what side on opening against resistance, why?

Answer 21

Deviation towards the damaged side
Lateral pterygoids open the jaw with downward and opposing force - no opposition to this force results in deviation to the weakened side