Muscles of Mastication

Question 1

What are the 4 muscles of mastication?

Answer 1

Temporalis
Masseter
Lateral pterygoid
Medial pterygoid

Question 2

Which nerve innervates the muscles of mastication?

Answer 2

CN V Trigeminal (v3 mandibular branch)

(brachial motor via trigeminal motor nucleus in rostral pons

Question 3

Describe the temporalis muscle

Answer 3

Large fan shaped muscle
Secondary mm of powerful chewing (after masseter)

PA: originates in temporal fossa
tendon passes under zygomoatic arch
DA: coronoid process & ramus of mandible
Actions: 
Bilateral - elevation and retrusion
Unilateral - ipsilateral excursion

Question 4

Describe the masseter muscle

Answer 4

Thick strong muscle running obliquely in a posterior & inferior direction
Primary muscle of powerful chewing

PA: zygomatic arch & zygomatic bone
DA: ramus of mandible

Bilateral - elevation
Unilalteral - slight lateral excursion

Question 5

Describe the lateral pterygoid muscle

Answer 5

Lateral pterygoid runs horizontally between sphenoid & mandible
Has a superior & inferior head

Superior head:
PA: greater wing of sphenoid
DA: TMJ capsule & medial disc

Inferior head:
PA: lateral pterygoid plate of sphenoid
DA: neck of mandible

Actions:
Bilateral - protrusion
Unilalteral - contralateral excursion

Superior head exerts antero-medial force on capsule and disc

Inferior head only -primary depressor of mandible

Question 6

Describe the medial pterygoid muscle

Answer 6

Similar line of force to masseter

PA: lateral pterygoid plate of sphenoid
DA: ramus of mandible

Bilateral - elevation and protrusion of mandible
Unilateral -contralateral excursion mandible

Question 7

Which muscles control the actions of the mandible?

Answer 7

Elevation -
Temporalis
Masseter

Depression - inferior head lateral pterygoid

Lateral excursion:
Ipsilateral - temporalis, masseter (unilateral)
Contralateral - pterygoids

Protrusion - pterygoids (bilateral)

Retrusion - temporalis