The document discusses the muscles of mastication. It describes the four primary muscles - masseter, temporalis, lateral pterygoid, and medial pterygoid. It details the origin, insertion, nerve supply, blood supply, actions and functions of each muscle. The document also briefly discusses secondary muscles like the suprahyoid muscles. Clinical considerations related to the muscles of mastication like tetanus, bruxism, and myofascial pain dysfunction syndrome are mentioned at the end.

1. MUSCLES OF MASTICATION
• DR.ASiF IQBAL
• 2nd Year P.G

2. CONTENTS
• INTRODUCTION
• DEFINITIONS
• MUSCLES OF MASTICATION
• CLINICAL CONSIDERATIONS OF MUSCLES
• REFERENCES

5. MASTICATION :
• Rhythmic opposition and separation of jaws with the
involvement of teeth ,lips ,cheeks and tongue for
chewing of food in order to prepare it for swallowing
and digestion.
• Main purpose of mastication is to reduce the size of
food particles to a size that is convenient for
swallowing (bolus formation) with the help of saliva.

6. MUSCLE OF MASTICATION
• The muscles which are required for mastication
are known as the muscles of mastication, These
muscles help mainly in the movement of the
mandible and not the maxilla as maxilla is an
integral part of the skull and the mandible being
the only movable bone in the skull.
• There are many muscles which help in the
process of mastication but the main muscles
which take part in the process are

7. PRIMARY MUSCLES OF
MASTICATION
• Masseter
• Temporalis
• Lateral pterygoid
• Medial pterygoid

8. SECONDARY MUSCLES OF
MASTICATION
• Suprahyoid
• Digastric
• Stylohyoid
• Mylohyoid
• Geniohyoid
• Infrahyoid muscles
• Sternohyoid
• Thyrohyoid
• Omohyoid

9. THESE MUSCLES ATTACHED TO
MANDIBLE ARE PRIMARILY
RESPONSIBLE FOR :
• ELEVATING
• DEPRESSING
• LATERAL MOVEMENT
• RETRUDING

10. • They are funtionally classified
as:
Jaw elevator
1. Masseter
2. Medial pterigoid
3. Temporalis
Jaw depresser
1. Lateral pterigoid
2. Digastric
3. Geniohyoid
4. Mylohyoid

12. LATERAL VIEW OF A FOUR WEEK EMBRYO SHOWING
MUSCLES DERIVED FROM BRANCHIAL ARCHES

13. COMMEN CHARATERSTIC OF
ALL MUSCLE OF
MASTICATION  All are inserted to the mandible.
 All are innervated by the mandibular division of
the trigeminal nerve.
 All are concerned for biting and chewing.
FUNCTIONS
To move the mandible.
To secure then stabilize the mandibular positions.
To determine the direction of mandibular
movements .

14. Masseter
• The masseter is a thick, somewhat
quadrilateral muscle, consisting of two parts,
superficial and deep. The fibers of the two
portions are continuous at their insertion. The
masseter muscle is sometimes the target of
plastic jaw reduction surgery.

18. • MIDDLE LAYER
• Origin -anterior 2/3 of the deep
surface and posterior 1/3 of the
lower border of the zygomatic arch,
• Insertion - middle part of ramus.
• DEEP LAYER:
• Origin -deep surface of the
zygomatic arch,
• Insertion - upper part of the
ramus and into the coronoid
process.

21. Origin : zygomatic arch and maxilla
Insertion : coronoid process, ramus of
mandible
Artery Supply :masseteric artery
Nerve supply : mandibular nerve (V3)
Actions : elevation (as in closing of the mouth)
and protraction of mandible

22. ACTIONS OF MASSETER
Actions:
• Elevates the mandible to close
the mouth and to occlude the
teeth in mastication.
• Its activity in the resting
position is minimal.
• It has a small effect in side-to-side
movement, protraction and
retraction.

25. Palpation
• The patient is asked to clench their teeth and,
using both hands, the practitioner palpates
the masseter muscles on both sides
extraorally, making sure that the patient
continues to clenchduring the procedure.
• Palpate the origin of the masseter
bilaterally along the zygomatic arch
and continue to palpate down the body of
the mandible where the masseter is attached

26. Palpate
multiple areas
of masseter
muscle

28. Clinical Importance of
Masseter Muscle of
Mastication:
• Masseter muscle can be palpated both intraorally and
extraorally
• The masseter muscle is sometimes the target of plastic jaw
reduction surgery.
• The muscle that commonly undergoes Hypertrophy in Bruxism
is Masseter
• Because of the Multipennate arrangement of fibers masseter is
a very powerful muscle

29. TEMPORALIS

30. Temporalis
 The temporal muscle, also known as the temporalis, is one
of the muscles of mastication. It covers much of the
temporal bone.
Structure :
 It arises from the temporal fossa and the deep part of
temporal fascia. It passes medial to the zygomatic arch and
inserts onto the coronoid process of the mandible.
 The temporal muscle is covered by the temporal fascia, also
known as the temporal aponeurosis.
 The muscle is accessible on the temples, and can be seen
and felt contracting while the jaw is clenching and
unclenching.

37. Origin and Insertion: From the Parietal bone of
the skull and is inserted on the coronoid process
of the mandible.
Arterial supply: The Deep Temporal artery
supplies the large muscle.
Nerve Supply: Trigeminal nerve( this nerve has
been associated with being the cause of
Headache and migrane.
Embryology :The temporalis is derived from the
first pharyngeal arch in development.

38. Functions:
• Elevation of the mandible
• Retraction of the mandible.
• Crushing of food between the molars.
• Posterior fibers draw the mandible backwards
after it has been protruded.
• It is also a contributor to side to side grinding
movement.

39. ACTIONS OF
TEMPORALIS
• Elevates the mandible, this
movement requires both the upward
pull of anterior fibers and backward
pull of the posterior fibers.
• Posterior fibers draw the mandible
backwards after it has been
protruded.
• It is also a contributory to side to
side grinding movement.

40. SIDE TO SIDE GRINDING
MOVEMENT

41. Palpation

42. Palpation
• To locate the muscle ,have the patient clench.
• Apply two pounds of pressure

44. Clinical Importance of
Temporalis Muscle:
• Sudden contraction of
temporalis muscle will result in
coronoid fracture, which is
rare.

45. LATERAL PTERYGOID

46. LATERAL PTERYGOID
ATTACHMENTS
 It is a short thick muscle with two parts
or head
• UPPER head arise from infratemporal
surface and infratemporal crest of
greater wing of sphenoid bone
• LOWER head arise from lateral surface
of lateral pterygoid plate.
• Its fibers pass backwards and laterally
to be inserted into a depression
(pterygoid fovea)on the front of the
neck of the mandible and into the
articular capsule and disc of the
temporomandibular articulation.

50. BLOOD SUPPLY
Pterygoid branch of
2nd part of maxillary
artery
NERVE SUPPLY
Nerve to lateral
pterigoid branch
anterior division of
trigiminal nerve

51. ACTIONS OF LATERAL
PTERYGOID
• Assists in opening the mouth with suprahyoid muscles.
• Right lateral pterygoid and right medial pterygoid turns the
chin to left side as a part of grinding movement.
• When the medial and lateral pterygoids of two sides act
together they protrude the mandible so that the lower incisors
project in front of the other.
• The upper (superior) head being involved in chewing

52. The combinded efforts of the
Digastrics and Lateral Pterygoids
provide for natural jaw opening.

53. SIDE TO SIDE GRINDING
MOVEMENT

54. Medial and lateral pterygoid act
together to protrude the
mandible

55. Palpation of Lateral
pterygoid

56. Medial Pterygoid
muscle

58. Medial Pterygoid
muscle:
• It is a thick muscle of mastication.
Origin and Insertion :
• It Arises lateral pterygoid plate, and from
the maxillary tuberosity.
• Insertion is seen on the Medial angle of
the Mandible

60. NERVE SUPPLY
• Branch of the main
trunk of the
mandibular nerve.
BLOOD SUPPLY
• Pterygoid branch of
2nd part of maxillary
artery

61. • Functions:
• Elevates the mandible.
• Closes the jaw.
• Helps in side to side movement.

64. Palpation of medial
pterigoid

65. Palpation of medial
pterygoid

66. • gently palpate them on the medial aspect of the jaw,
• simultaneously from both inside and outside the mouth

67. Clinical Importance of Medial
Pterygoid Muscle:
• Medial Pterygoid muscle can be
palpated only intraorally
• Most commonly involved in MPDS
• Trismus following inferior alveolar
nerve block is mostly due to
involvement of medial pterygoid
muscle

68. The 4 primary muscles of mastication are in turn supported
or supplemented by few secondary muscles known as
SUPRAHYOID GROUP of muscles they are
• DIGASTRIC
• MYLOHYOID
• GENIOHYOID

69. DIAGASTRIC MUSCLE
• Two bellies united by tendon
• The muscle has secondary role in mastication as a
depressor muscle adding to the action of lateral
pterygoid muscle when mouth is to be opened against
resistance.

70. MYLOHYOID MUSLE
• Flat triangular
• The secondary role of this muscle is evident as a
depressor seen in action when mouth is to be opened
against resistance.
• It elevates the floor of mouth to help in deglutition.

72. GENIOHYOID
• Short and narrow musle lies above
mylohyoid
• When the hyoid bone is fixed, it
depresses the mandible

73. GENIOHYOID MUSCLE

74. IMPORTANT FACTS ABOUT
MASTICATION
• There are about 15 chews in a series from the time of food
entry until swallowing
• Average jaw opening during chewing is between 16-20mm
• Average lateral displacement on chewing is between 3 and
5mm
• Men chew faster and have a shorter occlusal phase than
women, it also depends on the type of food

75. • CLINICAL
CONSIDERATIONS

76. TETANUS(LOCK JAW)
• Caused by exotoxins of gram positive bacillus Clostridium
tetani.
• Disease of the nervous system characterized by intense
activity of motor neuron and resulting in severe muscle
spasm
CLINICAL FEATURES
• Pain and stiffness in the jaws and neck muscles ,with
muscle rigidity producing trismus and dysphagia

77. TREATMENT
• All patients should receive antimicrobial drugs
• Active and passive immunization.
• Surgical wound care
• Anticonvulsant if indicated

78. BRUXISM
Bruxism : Jaw clenching, with or without forcible excursive movements,
where the intensity of the clenching dictates the severity (or lack of)
grinding .
Clenching- It can occur as a brief rhythmic strong contractions of the jaw
muscles during eccentric lateral jaw movements, or in maximum
intercuspation,
Causes
1) Associated with stressful events
2)Non stress related or hereditary

79. • Bruxism may lead to
-tooth wear
-fracture of the teeth or restoratrion
-uncosmetic muscle hypertrophy
• Treatment
-coronoplasty
-maxillary stabalization appliance

81. MYOFACIAL PAIN
DYSFUNCTION SYNDROME
• Pain
• Muscle tenderness
• Clicking in the joint
• Limitation in the mouth opening
TREATMENT
• Physiotherapy and Myotherapeutic exercises
• Transcutaneous Electronic Nerve Stimulation
• Muscle relaxants
• surgery

84. REFERENCES
• B.D.Chaurasias, Human anatomy
• Shafer,Hine,Textbook of oral
pathology
• Human anatomy A K Dutta
• Grays Anatomy
• Journal Refernces

85. THANK YOU