Muscles of Mastication

Question 1

What is the origin of the masseter?

Answer 1

zygomatic arch

Question 2

What is the insertion of the masseter?

Answer 2

lateral surface and angle of the mandible

Question 3

What is the action of the masseter?

Answer 3

elevate the mandible

Question 4

How do you examine the masseter?

Answer 4

• place one finger intra-orally
• place one finger extra-orally on the cheek
• palpate
• tenderness indicates a clenching habit (bruxism)

Question 5

What is the origin of the temporalis?

Answer 5

floor of the temporal fossa

Question 6

What is the insertion of the temporalis?

Answer 6

coronoid process and anterior border of the ramus

Question 7

What is the action of the temporalis?

Answer 7

elevates and retracts the mandible

Question 8

How do you examine the temporalis?

Answer 8

• palpate at the temples
• ask the patient to clench together
• tenderness indicates a clenching habit (bruxism)

Question 9

What is the origin of the lateral pterygoid?

Answer 9

lateral surface of the lateral pterygoid plate

Question 10

What is the insertion of the lateral pterygoid?

Answer 10

inferior belly = anterior border of the condyle

superior belly = intra-articular disc

Question 11

What is the action of the lateral pterygoid?

Answer 11

• protrudes and laterally deviates the mandible

- inferior head assists with the mandibular depressors

Question 12

What can cause a clicking noise during opening of the mouth?

Answer 12

superior head of the lateral pterygoid pulling on the intra-articular disc

Question 13

How do you examine the lateral pterygoid?

Answer 13

• not accessible to palpation
• response to resisted movement is used instead
• ask patient to move jaw laterally and push in the opposite direction and vice versa
• ask patient to move jaw vertically and push upwards
• pain = tenderness when palpated

Question 14

What is the origin of the medial pterygoid?

Answer 14

deep head = medial surface of the lateral pterygoid plate

superficial head = tuberosity of the maxilla

Question 15

What is the insertion of the medial pterygoid?

Answer 15

medial surfaces of the angle of the mandible

Question 16

What is the action of the medial pterygoid?

Answer 16

elevate and assist protrusion of the mandible

Question 17

How do you examine the medial pterygoid?

Answer 17

no reliable way to palpate or test this muscle

Question 18

Which muscle can cause trismus if contacted during IDB?

Answer 18

medial pterygoid

Question 19

Describe the movements of the TMJ.

Answer 19

• rotation = initial opening, rotation of the condyle, hinge movement
• translation = wider opening, sliding movement
• when the mandible protrudes, the condyles leave their fossae, and move along the articular eminences
• when the mandible retracts, the condyles leave the eminences and move back to their fossae

Question 20

What is Posselt’s envelope of motion?

Answer 20

• range of motion of the mandible

- sagittal view of the maximum mandibular movement

Question 21

Name the suprahyoid muscles.

Answer 21

• digastric
• mylohyoid
• geniohyoid
• stylohyoid

Question 22

Name in the infrahyoid muscles.

Answer 22

• sternohyoid
• omohyoid
• thyrohyoid
• sternothyroid

Question 23

Which muscles assist in the depression of the mandible?

Answer 23

• digastric
• mylohyoid
• geniohyoid
• lateral pterygoid

Question 24

Which facial muscles are involved in the control of bolus?

Answer 24

• orbicularis oris

- buccinator