Muscle of Mastication

mastication

• the process of chewing food in preparation for deglutition(swallowing) and digestion​

• Process by which food is crushed and ground by teeth.​

• The first step of digestion.​

• Increases the surface area of food to allow more efficientbreakdown by enzymes.​

• Is the repetitive sequence of jaw opening and closing witha profile in the vertical plane called CHEWING CYCLE.​

opening phase; closing phase; occlusal or intercuspal phase

3 Phases of CHEWING CYCLE are?​

opening phase

Mandible is depressed (phase)

closing phase

mandible is raised

occlusal or intercuspal phase

The mandible is stationary, and the teeth from both upper and lower arches approximate (phase)

elevation; depression; protrusion; retrusion; side-to-side (lateral) excursion

Movements of the mandible areclassified as:​

​All muscles of mastication originate on the skull and insert on the mandible; All muscles of mastication are innervated by the mandibular division of the trigeminal nerve​; All muscles of mastication are derivatives of the 1st pharyngeal arch​; All are concerned in biting and chewing.​

Muscles of Mastication (characteristics)

To move the mandible; To secure then stabilize the mandibular positions; To determine the direction of mandibular movements.​

Muscles of Mastication (functions)

Masseter

a flat quadrangular muscle, partlytendinous.​

Temporalis

a large, fan-shaped muscle at thesides of the head​

Lateral (External) Pterygoid

a thick andtriangular muscle with two heads.

Medial (Internal) Pterygoid

almost a mirror-like image of the masseter muscle​

Inferior border of theanterior 2/3 of the zygomaticarch​

origin of the masseter (superficial)

angle of the mandible, inferior and lateral parts of the mandibular ramus

insertion of the masseter (superficial)

elevates, protrudes, and aids in the lateral excursion of the mandible

action of the masseter (superficial)

masseteric branch - mandibular division - trigeminal nerve

nerve supply of the masseter

Medial border of the zygomatic arch, inferior border of the posterior 1/3 of the zygomatic arch​

origin of the masseter (deep)

Superolateral mandibular ramus, coronoid process​

insertion of the masseter (deep)

Elevates, protrudes, and aids in the lateral excursion of the mandible​

action of the masseter (deep)

Masseteric branch - mandibular division - trigeminal nerve​

nerve supply of the masseter (deep)

entire temporal fossa: along inferior temporal line including the temporal fascia​

origin of temporalis

coronoid process: along the apex, anterior and posterior borders, medial surface extending inferiorly on the anterior border of the mandibular ramus (temporal crest) to the third molar tooth

​insertion of the temporalis

elevates the mandible (anterior fibers), retrudes the mandible (posterior fibers), aids in lateral excursion of the mandible​

action of the temporalis

anterior and posterior deep temporal branches - mandibular division -trigeminal nerve​

nerve supply of the temporalis

temporalis

“The main postural muscles – maintains themandible in rest position.” ​

Greater wing of the sphenoid, Infratemporal crest​

origin of the Lateral (External) Pterygoid (upper head)​

Articular disc and capsuleof the TMJ​

insertion of the Lateral (External) Pterygoid (upper head)

Depresses, protrudes, lateral excursion of the mandible​

action of the Lateral (External) Pterygoid (upper head)

lateral pterygoid branches – mandibular division –trigeminal nerve​

nerve supply of the Lateral (External) Pterygoid (upper head)

Lateral surface of the lateral pterygoid plate​

origin of Lateral (External) Pterygoid (lower head)​

Pterygoid fovea on the neck of the condyle of the mandible ​

insertion of Lateral (External) Pterygoid (lower head)

Depresses, protrudes, lateral excursion of the mandible

action of Lateral (External) Pterygoid (lower head)

lateral pterygoid branches - mandibular division - trigeminal nerve​

nerve supply of Lateral (External) Pterygoid (lower head)

Maxillary tuberosity, pyramidal process of the palatine bone​

origin of Medial (Internal) Pterygoid (superficial head)​

Medial surface of the ramus and angle of the mandible (pterygoid tubercles)​

insertion of Medial (Internal) Pterygoid (superficial head)

Elevates, protrudes, lateral excursion of the mandible​

action  of Medial (Internal) Pterygoid (superficial head)

medial pterygoid branch-mandibular division-trigeminal nerve​

nerve supply of Medial (Internal) Pterygoid (superficial head)

Medial (Internal) Pterygoid (superficial head)​

“The deepest muscle of mastication.”​

Medial surface of the lateral pterygoid plate​

origin of Medial (Internal) Pterygoid (deep head)​

Medial surface of the ramus and angle of the mandible (pterygoid tubercles)​

insertion of Medial (Internal) Pterygoid (deep head)

Elevates, protrudes, lateral excursion of the mandible​

action of Medial (Internal) Pterygoid (deep head)

medial pterygoid branch - mandibular division - trigeminal nerve​

Nerve supply of Medial (Internal) Pterygoid (deep head)

Sphenomandibular Muscle​

This is one a part of the accessory ligament of TMJ,now regarded as the 5th muscle of mastication. It runs medial to the TMJ​

spine of sphenoid bone at the base of the skull​

origin of the Sphenomandibular Muscle

lingula on the mesial side of the ramus of the mandible​

insertion of the Sphenomandibular Muscle