Muscles Of Mastication

Question 1

Which branchial arch do the muscles of mastication derive from?

Answer 1

The first pharyngeal arch - mandibular arch

Question 2

What nerve supplies the muscles of mastication?

Answer 2

Mandibular division of trigeminal CNV3

Question 3

What attaches to the superior temporal line?

Answer 3

Temporal fascia

Question 4

Where does the temporalis originate?

Answer 4

Inferior temporal line

Question 5

Describe the fibres of the temporalis

Answer 5

Posterior fibres of temporalis run more horizontally than the anterior fibres which are running more vertically. These fibres come together to form a tendon which inserts onto the coronavirus process of the mandible.

Question 6

Function/action of separate temporalis posterior and anterior fibres

Answer 6

Vertical anterior fibres shorten to pull the mandible up = elevation
Horizontal posterior fibres shorten to pull the mandible back = retraction
Also aids in lateral excursion

Question 7

Clinical implications of the temporalis going quite far down the mandible?

Answer 7

Goes very close to mandibular molars, so implications in denture fittings. E.g., if temporalis fits too anteriorly then it can dislodge dentures.

Question 8

Innervation of temporalis

Answer 8

Anterior and posterior deep temporal branches of CNV3

Question 9

Blood supply to temporalis

Answer 9

Deep temporal arteries

Question 10

What are the 2 parts of the masseter and how do their fibres go?

Answer 10

Larger superficial head - fibres to posterior-inferiorly, aids in mandible protrusion
Smaller deeper head - fibres go more vertically

Question 11

What do both parts of the masseter aid in?

Answer 11

Elevation of mandible, powerfully closing mouth. Aid in lateral excursion.
(superficial part helps protrude the mandible)

Question 12

Origin and insertion of masseter

Answer 12

Origin: zygomatic arch
Insertion: lateral ramus and angle of the mandible

Question 13

Innervation of masseter

Answer 13

Masseteric branch of CNV3 (anterior division)

Question 14

Action of the lateral pterygoid

Answer 14

Lateral pterygoid muscles act to bring the condylar head of the mandible forward by protrusion and then rotation to depress the mandible.

Question 15

Origin and insertion (and main function) of lateral pterygoid superior head

Answer 15

Origin: greater wing of sphenoid
Insertion: capsule and articular disc of TMJ
Action: protrusion

Question 16

Origin and insertion (and main function) of lateral pterygoid inferior head

Answer 16

Origin: lateral surface of lateral pterygoid plates
Insertion: pterygoid fovea on neck of condylar process of mandible
Action: depression

Question 17

Innervation of lateral pterygoids

Answer 17

Nerve to lateral pterygoid, anterior division of CNV3

Question 18

Origin of medial pterygoid superficial head

Answer 18

Origin on maxillary tuberosity (posterior aspect of maxilla) and pyramidal process of palatine bone

Question 19

Origin of medial pterygoid deep head

Answer 19

Origin on medial surface of lateral pterygoid plate

Question 20

Insertion of the medial pterygoid

Answer 20

Superficial and deep heads come together to form a tendon and insert onto the medial surface of the angle of the mandible.

Question 21

Actions of the medial pterygoids

Answer 21

Elevation, protrusion, lateral excursion

Question 22

Innervation of medial pterygoids

Answer 22

Medial pterygoid nerve from main trunk of CNV3

Question 23

Summary of muscles causing depression, elevation, retraction and protrusion of the mandible

Answer 23

Depression: lateral pterygoids, digastric, mylohyoid, geniohyoid
Elevation: temporalis, masseter, medial pterygoid
Retraction: posterior fibres of temporalis, deep part of masseter, geniohyoid and digastric
Protrusion: lateral pterygoid assisted by medial pterygoid and masseter

Question 24

What happens in dissolution of the TMJ?

Answer 24

Condylar head comes out of the mandibular fossa, anterior to the articular tubercle.

Question 25

Clinical correlations of the muscles of mastication

Answer 25

Bruxism, TMD