The document discusses the muscles of mastication, which are a group of muscles that attach to the mandible and are involved in chewing by facilitating movements of the temporomandibular joint. It describes the four main muscles - the masseter, temporalis, medial pterygoid, and lateral pterygoid muscles. Each muscle is outlined, including its origin, insertion, nerve innervation, blood supply, and main actions. The document also briefly mentions trismus, a pathology involving reduced opening of the jaws that can be caused by spasm of the masticatory muscles or infection spread into the surrounding fascia.

1. MUSCLES OF
MASTICATION
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Prepared By: Mohsen M. Mirkhan

2. MASTICATION
 Is the voluntary process of grinding and chewing
food into smaller pieces in the oral cavity turning it
into a food bolus so it becomes soft enough to
swallow.
 Allow the initial stages of digestion to occur by the
enzymes in the saliva.
 Masticatory muscles partake in specific
movements of the temporomandibular joint (TMJ)
during this process.
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3. Muscles of Mastication
A group of muscles associated with movements of the jaw
(temporomandibular joint).
 Their main function is chewing
 All of them are attached to the mandible
 They are concerned with:
 Bite
 Side to side movement
 Chewing of the food
 Secure then stabilize the mandible position
 develop from the first pharyngeal arch.
 innervated by the mandibular nerve (V3) which is a
branch of the trigeminal nerve (CN 5).
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4. MUSCLES OF
MASTICATION
1) Masseter muscles
2) Temporalis muscles
3) Medial pterygoid muscles
4) Lateral pterygoid muscles
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5. MASSETER MUSCLE
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 the most powerful muscle of mastication, Thick, somewhat quadrilateral
muscle.
 can be split into two parts; Deep and Superficial.
 Action: Elevates the mandible, closing the mouth
 Nerve supply
 Blood supply
Masseteric never branch of mandibular nerve V3
Masseteric artery from maxillary artery

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7. TEMPORALIS MUSCLE
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 It’s a large fan-shaped muscle. is a broad, radiating muscle, situated at the
side of the head.
 Originates from the temporal fossa.
 Action: Elevates the mandible, retracts the mandible, pulling the jaw
posteriorly.
 Nerve supply
 Blood supply
Deep temporal branches of mandibular nerve.
Deep temporal branches of maxillary artery

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9. LATERAL PTERYGOID MUSCLE
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 Has two heads: Superior and Inferior.
 Action: acting together they protrude and depress the mandible.
produce side to side movements.
 Innervation: Ant. division of mandibular nerve through lateral pterygoid nerve.
 Blood supply: Maxillary artery through the pterygoid branch.
 Origin: Superior arises from greater wing of sphenoid bone
Inferior arises from the lateral surface of the lateral pterygoid plate
 Insertion: Fibers pass backward to be inserted into the neck of mandible and
articular disc of TMJ.

10. MEDIAL PTERYGOID MUSCLE
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 Has two heads: Superior and Deep.
 Action: assets in elevating and protrusion of the mandible
acts together with lat. Pterygoid of the same side in rotating the
mandible.
 Innervation: Main trunk of mandibular nerve through nerve to medial pterygoid
 Blood supply: Maxillary artery through the medial pterygoid artery
 Origin: Superior arises from the maxillary tuberosity.
Deep arises from medial surface of the lateral pterygoid plate
 Insertion: fibers run downward, backward and laterally and are inserted into the
medial surface of the angle of the mandible.

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13. PATHOLOGY
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Trismus : refers to reduced opening
of the jaws caused by spasm of the
muscles of mastication, or may generally
refer to all causes of limited mouth
opening.
 The affected patients find it very difficult
and in some cases impossible to open
the mouth.
 The muscles are usually not the primary
cause, however they can be included in
the problem due to the spread of dental
infection into the fascias that surround
them.

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