notes on muscles of mastication for examination purpose .

1. z
MUSCLE OF
MASTICATION
DR. SONAL SUBHANGI { MDS1ST YEAR}

2. z CONTENT
 INTRODUCTION
 EMBRYOLOGY
 BLOOD SUPPLY AND LYMPHATICS
 NERVES
 MUSCLES
 CLINICAL SIGNIFICANCE
 PREVALENCE
 REFERENCES

3. z INTRODUCTION
The primary muscles of mastication (chewing food) are the temporalis, medial
pterygoid, lateral pterygoid, and masseter muscles.
The four main muscles of mastication attach to the rami of the mandible and
function to move the jaw (mandible).
The cardinal mandibular movements of mastication are elevation, depression,
protrusion, retraction, and side to side movement.
To augment the process of eating, the muscles of mastication also move the
mandible in a side to side motion to assist in the grinding of food.
The muscles of mastication also function to approximate (bring together or close)
the teeth.
The superficial muscle of the neck, the platysma muscle, also assists with
depression of the mandible against resistance.

4. z EMBRYOLOGY
The muscles of mastication arise from the first pharyngeal arch.
They are then differentiated into muscles starting the seventh week. The nerve
supply to these muscles begins by the eighth week

5. z
BLOOD SUPPLY AND LYMPHATICS
The arterial supply to the muscles of mastication is via the maxillary artery, a branch
of the external carotid artery.

6. z NERVES
The four main muscles of mastication are all innervated by the anterior trunk of the mandibular
nerve, which is the third division of the trigeminal nerve (CN V3).
The mandibular nerve (CN V3) is the largest and inferior-most division of the trigeminal nerve (CN
V).
The trigeminal nerve (CN V) exits the skull via foramen ovale of the greater wing of the sphenoid
bone. The mandibular nerve contains both sensory and motor fibers.
The mandibular nerve is the only division of the trigeminal nerve that carries motor fibers.
The mandibular nerve (CN V3) further subdivides as it innervates the four main muscles of
mastication.
The temporalis muscle receives innervation by deep temporal branches of the mandibular nerve.
The medial pterygoid muscle receives innervation from the medial pterygoid nerve, a division of
the mandibular nerve .
The lateral pterygoid muscle gets its nerve supply from the lateral pterygoid nerves, divisions of
the mandibular nerve. The masseter muscle receives nerve input from the masseteric nerve, a
division of the mandibular nerve.

7. z MUSCLES
The primary and accessory muscles of mastication work in a coordinated fashion to
produce mandibular movement for chewing food.
The accessory muscles of mastication are the buccinator, suprahyoid muscles (digastric
muscle, mylohyoid muscle, and geniohyoid muscle), and infrahyoid muscles (the
sternohyoid, sternothyroid, thyrohyoid and omohyoid muscle).
The origin, insertion, and action of the main muscles of mastication, as well as a brief
description of the accessory muscles of mastication, are as follows .
Mainly 4 muscles:
Masseter
Temporalis
Lateral pterygoid
Medial pterygoid

8. z

9. z Temporalis Muscle
The temporalis muscle is a fan-shaped muscle with anterior fibers that have a vertical
orientation, mid fibers have an oblique orientation, and posterior fibers have a more of a
horizontal orientation.
ORIGIN INSERTION NERVE SUPPLY ACTIONS
From whole length of
temporal fossa.
Fibres converge
downwards.
Anterior fibers – descend
vertically .
Intermediate – obliquely .
Posterior fibers –
horizontally to get inserted
into the coronoid process
& anterior margin of ramus
of mandible .
Some fibres also join
masseter and pass on to
mandible.
By deep temporal
branches of the anterior
trunk of mandibular nerve.
Elevates mandible .
Posterior fibres retract the
mandible after protraction .
Helps in lateral sliding of
mandible during grinding.

10. z Lateral Pterygoid
The lateral pterygoid muscle is the primary muscle of the inferior temporal fossa.
The lateral pterygoid has two parts: an upper head and a lower head .
ORIGIN INSERTION NERVE SUPPLY ACTIONS
upper head – arises
from infra temporal
surface and infra
temporal crest of
greater wings of
sphenoid.
Lower head – arises
from lateral surface of
lateral pterygoid plate
of sphenoid .
Depression in front of
the neck of mandible.
Articular disc of
temporomandibular
joint.
By a branch of
mandibular nerve.
Protrusion of
mandible along with
medial ptergygoid.

11. zMedial Pterygoid
The medial pterygoid muscle is a thick rectangular muscle with a superficial head and
a deep head.
ORIGIN INSERTION NERVE SUPPLY ACTION
Superficial part – from
the medial surface of
lateral pterygoid plate .
From the grooved
surface of the pyramidal
surface of palatine bone.
Deep part – small slip
originates from lateral
surfaces of palatine bone
and tuberosity of maxilla.
into the lower and back
part of the medial
surfaces of angle and
ramus of mandible as
high as mandibular
foramen above & nearly
as forward as mylohyoid
groove.
By a branch of
mandibular nerve.
Assist in protrusion of
mandible.
Acting with lateral
pterygoid alternatively , it
produces a movement .

12. z Masseter
The masseter muscle is a rectangularly shaped muscle with three layers (superficial,
deep, and intermediate).
ORIGIN INSERTION NERVE SUPPLY ACTION
Superficial layer – its
fibres originate from
zygomatic process of
maxilla in the form of a
thick aponeurosis .
Anterior 2/3rd of the
lower border of
zygomatic arch.
Middle layer – deep
surfaces of anterior 2/3rd
of arch. Lower border of
posterior 1/3rd of arch.
Deep layer – from the
deep surface of
zygomatic arch.
Superficial layer –
downwards and
backwards into the angle
and lower half of the
lateral surfaces of
mandible.
Middle layer- into the
middle part of ramus.
Deep layer – into the
upper part of ramus and
coronoid process.
Masseteric nerve ,
branch of the anterior
trunk of mandibular
nerve.
Elevation of mandible

13. z

14. z Accessory Muscles of Mastication
The strap muscles are composed of the suprahyoid, and infrahyoid muscles are
located on the side of the neck bilaterally.
The strap muscles primarily function to raise and depress the hyoid bone and
larynx.
The strap muscles also assist with depression of the mandible when opening the
mouth against an opposing force.
The buccinator is a facial expression muscle that helps in mastication by keeping
food pushed back within the oral cavity.

15. z CLINICAL SIGNIFICANCE
Masticatory muscle disorders include myofascial pain and dysfunction, myositis, and
neoplasms.
Myofascial pain and dysfunction may result from several etiologies.
The most common ones are nocturnal bruxism, habitual clenching of the mouth, and
whiplash injuries during a trauma.
Temporomandibular joint (TMJ) dysfunction can result from an imbalance of forces
within the muscles of mastication.
Grinding of teeth at night (bruxism) is a common cause of TMJ dysfunction secondary
to a resultant imbalance in the muscle of mastication forces from excessive grinding of
the teeth.
Muscle spasm of the muscles of mastication (trismus) can be a symptom of tumor or
infection.

16. z
An infection like tetanus may present with "lockjaw" or trismus.
Other infections or inflammation of the muscles may present as myositis or pain
during the movement of the jaw.
Tumors, although rare but may present in the masticator space, which
is enveloped by the deep cervical facia.
These tumors may have an extension from adjacent regions.
The medial side of the fascia is attached to the skull base, and the lateral side
extends to the temporalis muscle.
Anteriorly it is attached to the body of the mandible at the level of the oblique line,
and posteriorly it is attached to the ramus of the mandible.

17. z PREVALENCE
The sample population included 199 participants (66% female and 34% male). The
prevalence of TMD-related pain was 26.8% (n = 42); men and women did not differ
statistically in their TMD-related pain.
Alkhubaizi Q , Khalaf M E and Faridoun A . Prevalence of Temporomandibular Disorder-Related Pain
among Adults Seeking Dental Care: A Cross-Sectional Study . Int J Dent . 2022 Sep ; 3186069.

18. z REFERENCES
 Standring S . Gray's Anatomy :The Anatomical Basis of Clinical
Practice . 42th Edition.
 Selvakumari T L . Essentials of Anatomy for Dental Students . 1st
Edition.
 Chaurasia B D & Garg K . B D Chaurasia's Human Anatomy . 9th
Edition .
 Devi V S . Inderbir Singh's Textbook of Anatomy for Dental Students .
7TH Edition.

19. z