M+O 2 - muscles of mastication

Question 1

What makes up the TMJ?

Answer 1

• condyle
• glenoid fossa
• articular eminence

Question 2

What is the physiological chewing force (dentate)?

Answer 2

70-150N

Question 3

What is the physiological chewing force (edentulous)?

Answer 3

4-55N

Question 4

What is the maximum clenching force between molars?

Answer 4

500-700N

(record: 4,345N - 37yo male, bruxist, hypertrophied masseter and temporalis)

Question 5

What are the 3 groups of muscles involved in mastication?

Answer 5

• between skull and mandible (muscles of mastication)
• between mandible and hyoid
• hyoid stabilisers

Question 6

What are the muscles of mastication (between the skull and the mandible)?

Answer 6

• masseter
• temporalis
• medial pterygoid
• lateral pterygoid

Question 7

What is the origin of the superficial masseter?

Answer 7

zygomatic arch/bone

Question 8

What is the insertion of the superficial masseter?

Answer 8

angle/ramus of mandible

Question 9

What is the action of the superficial masseter?

Answer 9

• jaw elevation (closing)
• minor protrusion

Question 10

What is the origin of the deep masseter?

Answer 10

inner aspect of zygomatic arch

Question 11

What is the insertion of the deep masseter?

Answer 11

angle/ramus of mandible

Question 12

What is the action of the deep masseter?

Answer 12

jaw elevation (closing)

Question 13

What is the origin of the temporalis?

Answer 13

inferior temporal line and fascia

Question 14

What is the insertion of the temporalis?

Answer 14

coronoid process

Question 15

What is the action of the temporalis?

Answer 15

jaw elevation and retrusion (posterior fibres)

Question 16

What is the origin of the upper head of lateral pterygoid?

Answer 16

infratemporal surface of greater wing of sphenoid

Question 17

What is the insertion of the upper head of lateral pterygoid?

Answer 17

capsule and articular disc of TMJ

Question 18

What is the origin of the lower head of lateral pterygoid?

Answer 18

lateral aspect of lateral pterygoid plate

Question 19

What is the insertion of the lower head of lateral pterygoid?

Answer 19

pterygoid fovea below head of condyle

Question 20

What is the function of the inferior head of lateral pterygoid?

Answer 20

• pulls condyle forwards
• bilateral : protrusion and assists opening
• unilateral : lateral excursion

Question 21

What is the function of the superior head of lateral pterygoid?

Answer 21

• active during retrusion and closing

Question 22

What are the origins of medial pterygoid?

Answer 22

• medial aspect of lateral pterygoid plate
• maxillary tuberosity

Question 23

What is the insertion of medial pterygoid?

Answer 23

medial aspect of ramus/angle of mandible

Question 24

What is the action of medial pterygoid?

Answer 24

• jaw elevation
• assists protrusion and lateral excursions (unilateral)

Question 25

What are the muscles between the mandible and the hyoid?

Answer 25

- geniohyoid - mylohyoid - digastric (anterior belly)

Question 26

What is the origin of geniohyoid?

Answer 26

inferior mental spine and inferior genial tubercle

Question 27

What is the action of geniohyoid?

Answer 27

- hyoid fixed : jaw opening (+ retrusion) - hyoid not fixed: raise ( + forward) hyoid

Question 28

What is the origin of the mylohyoid?

Answer 28

mylohyoid line (on mandible)

Question 29

What is the action of the mylohyoid?

Answer 29

- hyoid fixed: jaw opening - hyoid not fixed: raise hyoid and FOM

Question 30

What is the origin of anterior belly of digastric?

Answer 30

digastric fossa

Question 31

What is the action of anterior belly of digastric?

Answer 31

- hyoid fixed: jaw opening - hyoid not fixed: raise hyoid

Question 32

What are the hyoid stabiliser muscles?

Answer 32

- infrahyoids - thyrohyoid - omohyoid - sternohyoid - posterior belly of digastric - stylohyoid

Question 33

What other muscles are involved in mastication?

Answer 33

- obicularis oris - buccinator