The document describes the muscles of mastication. It notes that these muscles develop from the mesoderm of the first pharyngeal arch and are innervated by the mandibular division of the trigeminal nerve. The muscles are classified as jaw elevators or depressors. Key jaw elevator muscles include the masseter, temporalis, and medial and lateral pterygoid muscles. The lateral and medial pterygoid are also involved in jaw depression, protrusion and side to side movement.

1. By:
Sharmin Susiwala
SY BPT
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2.  Muscles of mastication develop from the
mesoderm of the first pharyngeal arch.
 They are innervated by the Mandibular
division of the trigeminal nerve.
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3.  They are functionally classified as:
 Jaw elevators:
 Masseter
 Temporalis
 Medial pterygoid
 Upper head of lateral pterygoid
 Jaw depressors
 Lower head of lateral pterygoid
 Anterior digastric
 Geniohyoid
 Mylohyoid
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4.  It has 3 layers:
 Superficial layer:
 Origin: lower border of the zyg.arch(ant 2/3)
 Insertion: lateral surface of the ramus
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5.  Middle layer:
 Origin: Medial surface of the anterior 2/3
Lower border of the posterior 1/3 of zyg arch.
 Insertion: lateral surface of the ramus
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6.  Deep layer:
 Origin: Medial surface of zygomatic arch
 Insretion: upper part of the ramus
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7.  Action:
 Elevation (deep fibers)
 Protraction (superficial fibers)
 Nerve supply:
 Anterior division of mandibular nerve (masseteric
nerve)
 Blood supply:
 Transverse facial artery
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9.  Has 2 heads:
 Deep head (anterior, middle and
posterioe fibers)
 Superficial head (much smaller)
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10.  Origin: Temporal fossa, Temporal fascia
 In an area bound by the inferior temporal line above and the
infra temporal crest below
 Insertion:
 Cronoid process in its medial aspect (apex, anterior and
posterior border)
 Anterior border of the ramus.
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11.  Action:
 Elevation (anterior fibers)
 Protraction (posterioe fibers)
 Nerve supply:
 Anterior division of the mandibular nerve
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13.  Has 2 heads:
 Upper head:
 Origin: infratemporal surface & crest of the greater wing of sphenoid
 Insertion: enters the TMJ & inserted into:
a) ptrygoid fovea of the neck of the mandible
b) articular disc
c) capsule of TMJ (anterior aspect)
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14.  Lower head:
 Origin: Lateral surface of the lateral
pterygoid plate
 Insertion: as upper head
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15.  Action:
1. Both muscles produce
depression of the mandible.
2. Lat. & Med pterygoid on 1 side protrude
the mandible to the
opposite side.
3. Lat & Med pterygoid on the 2 sides cause
side to side movement
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16.  Nerve supply: Anterior division of mandibular
nerve (nerve to lateral pterygoid)
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18.  Has 2 heads
 Superficial head:
 Origin: a) maxillary tuberosity
b) neighboring part of palatine
bone.
_ Insertion: Medial surface of the angle &
ramus below the mandibular
foramen.
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20.  Deep head:
 Origin: Medial surface of the lateral
pterygoid plate.
 Insertion: as upper head.
 Action: 1) both muscles elevate the
mandible.
2 & 3 as in lateral pterygoid.
 Nerve supply: Trunk of the mandibular
nerve (nerve to
medial pterygoid
muscle)
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23. Thank You
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