Oral Biology: Muscles of Mastication

Question 1

What does “mastication” mean?

Answer 1

Chewing

Question 2

What does the breakdown of food stuffs via mastication involve? (3)

Answer 2

1) preparation for swallowing
2) increase surface area for chemical digestion
3) release of chemicals for sense of taste

Question 3

What is stimulated by mastication?

Answer 3

salivary flow

Question 4

Where do masticatory movements take place?

Answer 4

The temporomandibular joint (TMJ)

Question 5

What does the TMJ comprise of?

Answer 5

1) Glenoid Fossa of the Temporal Bone
2) Articular Eminence
3) Condyle of the Mandible

Question 6

What movement occurs at the TMJ with a slight jaw opening?

Answer 6

A simple hinge movement

Question 7

What movement occurs at the TMJ with a wide jaw opening?

Answer 7

Hinge and Slide

Question 8

What movement occurs at the TMJ when the jaw protrudes?

Answer 8

Slide movement

Question 9

What three groups of muscles are involved in mastication?

Answer 9

1) Muscles between the skull and mandible
2) muscles between mandible and hyoid
3) hyoid stabilisers

Question 10

What group of muscles acts across the TMJ and is considered the main group of muscles of mastication?

Answer 10

Muscles between the skull and the mandible

Question 11

Name the four muscles under the “Skull-Mandible” group

Answer 11

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

Question 12

What is the:

1) origin
2) insertion

of the SUPERFICIAL MASSETER?

Answer 12

1) Origin: zygomatic arch/bone

2) Insertion: angle/ramus of the mandible

Question 13

What is the action of the superficial masseter muscle?

Answer 13

Jaw elevation (closing), minor protrusive action

Question 14

What nerve innervates the superficial masseter?

Answer 14

Masseteric nerve of the Motor Root of CNVc

Question 15

What is the:

1) origin
2) insertion

of the DEEP MASSETER?

Answer 15

1) Origin: Inner aspect of the zygomatic arch

2) Insertion: angle/ramus of the mandible

Question 16

What is the action of the deep masseter muscle?

Answer 16

Jaw elevation (closing)

Question 17

What is the innervation of the deep masseter muscle?

Answer 17

Masseteric nerve of the motor root of CNVc

Question 18

What is the:

1) origin
2) insertion

of the TEMPORALIS?

Answer 18

1) Origin: inferior temporal line and fascia

2) Insertion: coronoid process

Question 19

What is the action of the Temporalis muscle?

Answer 19

Jaw elevation and retrusion (due to it’s posterior fibres)

Question 20

What innervates the Temporalis muscle?

Answer 20

Deep Temporal Nerve of the Motor Root of CNVc

Question 21

What is the:

1) origin
2) insertion

of the UPPER HEAD of the LATERAL PTERYGOID?

Answer 21

1) Origin: Infratemporal surface of the greater wing of sphenoid
2) Insertion: capsule and articular disc of TMJ

Question 22

What is the:

1) origin
2) insertion

of the LOWER HEAD of the LATERAL PTERYGOID?

Answer 22

1) Origin: lateral aspect of the lateral pterygoid plate

2) Insertion: pterygoid fovea below head of condyle

Question 23

What is the action of the lateral pterygoid?

Answer 23

A complex action which ultimately leads to jaw opening.
Initial opening: hinge in lower joint space with help from suprahyoids only.
Wide opening: anterior and inferior translation of condyle assisted by inferior lateral pterygoids

Question 24

What innervates the lateral pterygoid?

Answer 24

CNVc motor root - nerve to lateral pterygoid

Question 25

What does the inferior head of the lateral pterygoid do: 1) bilaterally? 2) unilaterally?

Answer 25

Bilaterally: 1) pulls condyle forward 2) assists opening 3) protrusion Unilaterally: 1) facilitates lateral excursion

Question 26

When is the superior head of the lateral pterygoid active?

Answer 26

During retrusion and closing

Question 27

What is the: 1) origin 2) insertion of the MEDIAL PTERYGOID?

Answer 27

1) Origin: medial aspect of lateral pterygoid plate of the sphenoid bone and maxillary tuberosity 1) Insertion: Medial aspect of ramus/angle of the mandible

Question 28

What is the action of the medial pterygoid? (2)

Answer 28

1) jaw elevation | 2) assists protrusion and lateral excursions (unilateral)

Question 29

What innervates the medial pterygoid muscle?

Answer 29

CNVc Motor Root - nerve to medial pterygoid

Question 30

What are the three muscles that fall under the Mandible-Hyoid group?

Answer 30

1) Geniohyoid 2) Mylohyoid 3) Digastric (anterior)

Question 31

What is the: 1) origin 2) insertion of the geniohyoid muscle?

Answer 31

1) Origin: inferior mental spine and inferior genial tubercle 2) Insertion: Hyoid bone

Question 32

What is the action of the geniohyoid muscle when: 1) the hyoid is fixed 2) the hyoid is not fixed

Answer 32

1) hyoid fixed: jaw opening (and retrusion) | 2) hyoid not fixed: raise (and forward) hyoid

Question 33

What innervates the geniohyoid muscle?

Answer 33

C1 spinal nerve (with hypoglossal)

Question 34

What is the: 1) origin 2) insertion of the MYLOHYOID muscle?

Answer 34

1) Origin: mylohyoid line of the mandible | 2) upper border of the hyoid bone

Question 35

What innervates the mylohyoid muscle?

Answer 35

CNVc Motor Root - nerve to mylohyoid

Question 36

What is the raphe that lies inferiorly to the mylohyoid muscle called?

Answer 36

the median raphe

Question 37

What is the action of the MYLOHYOID muscle when: 1) hyoid is fixed? 2) hyoid is not fixed?

Answer 37

1) Hyoid Fixed: jaw opening | 2) Hyoid not fixed: raise hyoid and floor of mouth

Question 38

What is the: 1) origin 2) insertion of the anterior belly of digastric?

Answer 38

1) Origin: Digastric Fossa of the mandible | 2) Insertion: intermediate tendon (secured to the hyoid bone by a fibrous loop

Question 39

What is the action of the anterior belly of digastric when: 1) hyoid is fixed 2) hyoid is not fixed

Answer 39

1) Hyoid fixed: jaw opening | 2) Hyoid not fixed: raise hyoid

Question 40

What innervates the anterior belly of digastric?

Answer 40

CNVc Motor Root - via nerve to mylohyoid

Question 41

What are the three muscles that fall under the "Hyoid Stabliser" group?

Answer 41

1) Infrahyoids (thyrohyoid, omohyoid, sternohyoid) 2) Posterior Digastric 3) Stylohyoid

Question 42

What other two muscles are involved in mastication?

Answer 42

1) obicularis oris (oral sphincter) | 2) buccinator (along with the tongue, helps control the bolus of food and direct it to posterior teeth)

Question 43

What are the physiological chewing forces (N) in: 1) dentate patients? 2) edentulous patients?

Answer 43

1) dentate patients: 70-150N | 2) edentulous patients: 4-55N

Question 44

What is the maximum clenching force between molars (N)?

Answer 44

500-700N