Muscles of Mastication

What are the layers of the masseter muscle

3 layers, superficial, middle, deep

Masseter muscle

Insertion

Fibers run downward & backward at a 45’ angle. Attach to outer aspect of ramus (of the mandible). Deep layer attaching to rest of ramus

Masseter muscle

Nerve supply

Masseteric nerve (branch of mandibular nerve)

Masseter muscle

Action

Elevation of mandible. Slight protrusion

Superficial head of masseter muscle origin

Anterior two thirds of lower border of zygomatic arch & adjoining zygomatic process

Middle layer of masseter muscle origin

Lower border of posterior one third of zygomatic arch

Deep layer of masseter muscle origin

Deep surface of zygomatic arch

Temporalis muscle

Origin

Temporal fossa & temporal fascia

Temporalis muscle

Insertion

Runs vertically downward. Inserts at coronoid process & anterior border of ramus (of the mandible)

Temporalis muscle

Nerve supply

Temporal branches of mandibular nerve

Temporalis muscle

Action

Elevation & retraction of mandible. Contributes to side to side

Medial pterygoid muscle

Layers

Two layers, superficial & deep

Medial pterygoid muscle

Insertion

Fibers run downward & backward. Attach at medial surface of angle & ramus (of the mandible)

Medial pterygoid muscle

Nerve supply

Nerve to medial pterygoid (branch of mandibular nerve)

Medial pterygoid muscle

Action

Elevation & protrusion of mandible. Assists in side to side

Origin of superficial head of medial pterygoid muscle

Maxillary tuberosity

Origin of deep head of medial pterygoid muscle

Medial surface of lateral pterygoid plate

Lateral pterygoid muscle

Layers

Two layers, upper & lower

Lateral pterygoid muscle

Insertion

Runs backward & laterally. Attaches at pterygoid fovea, anterior margin of articular disc & capsule of TMJ

Lateral pterygoid muscle

Nerve supply

Branches from anterior division of the mandibular nerve

Lateral pterygoid muscle

Action

Only muscle that depresses mandible (during mouth opening). Protrusion of mandible & assists side to side movements

Origin of upper head of lateral pterygoid muscle

Intratemporal fossa

Origin of lower head of lateral pterygoid muscle

Lateral surface of lateral pterygoid plate

Which muscle depresses mandible

Lateral pterygoid muscle

Which muscle is below and behind mandibular foramen

Medial pterygoid muscle