applied anatomy of muscle of mastication

1. MUSCLES OF MASTICATION
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Sauvik Singh
P.G Resident 1st year
HDCH

2. INTRODUCTION
EMBRYOLOGY
HISTOLOGY
MUSCLES OF MASTICATION
MASSETER
TEMPORALIS
MEDIAL PTERYGOID
LATERAL PTERYGOID
ACCESSORY MUSCLES OF MASTICATION
APPLIED ASPECTS
CONCLUSION
REFERENCES
CONTENTS
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3. MUSCLE- One of the contractile organs of the body
OR
Animal tissue consisting predominantly of contractile cells
Mastication or chewing is the process by which food is mashed
and crushed by teeth. During the mastication process, the food
is positioned between the teeth for grinding by the cheek and
tongue .
INTRODUCTION
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4. Most muscle fibers develop before birth but increase in
number and size in early infancy.
Motor nerves establish contact with the myocytes,
stimulating their activity and further growth by
hypertrophy.
Failure of nerve contact or activity results in muscle atrophy
EMBRYOLOGY
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5. Mesodermal Origin Muscles Innervation (Cranial Nerve)
Somitomeres 1,2 Superior, inferior, and medial ocular recti;
inferior oblique of eye Oculomotor (III)
Somitomere 3 Superior oblique of eye Trochlear (IV)
Somitomere 4 1st-arch masticatory muscles Trigeminal (V)
Somitomere 5 Lateral ocular rectus Abducens (VI)
Somitomere 6 2nd-arch facial muscles Facial (VII)
Somitomere 7 3rd-arch stylopharyngeus0 Glossopharyngeal
(IX)
Somites 1,2 Laryngeal muscles Vagus (X)
Somites 1–4 Tongue muscles Hypoglossal (XII)
Somites 3–7 Sternomastoid, trapezius Accessory (XI)
CRANIOFACIAL MUSCLE ORIGINS AND
INNERVATIONS
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6. According to morphology-
Striated, non striated, smooth
According to function-
Voluntary, involuntary
Types-
Skeletal- striated & voluntary
Cardiac- striated & involuntary
Smooth- non striated & involuntary
HISTOLOGY
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7. HISTOLOGY
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8. Skeletal-
Elongated and tubular, multiple nuclei located in periphery.
Striated muscle has alternating light and dark bands
Cardiac-
not long as skeletal & are branched cells.
Mono or bi nucleated located in center, striated, intercalated.
Smooth-
Spindle shaped, wide in middle & narrow at both ends,
Single centrally located nucleus.
No visible striation, but has same contractile protein
CHARACTERISTICS
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9. No capability of mitotic activity, regeneration by satellite cells.
If undergo mitotic activity- hyperplasia.
Muscle building, satellite cells may fuse with existing muscle cells,
thus hypertrophy.
Skeletal muscle cells regulate their number and their size by the
secretion of a member of the transforming growth factor-β
(TGF-β), myostatin
REGENERATION OF MUSCLE
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10. Mastication is a repetitive sequence of jaw opening and closing
with a profile in the vertical plane called the chewing cycle.
Mastication consists of a number of chewing cycles. The
human chewing cycle consists of three phases:
1. Opening phase: the mouth is opened and the mandible is
depressed.
2. Closing phase: the mandible is raised towards the maxilla.
3. Occlusal or intercuspal phase: the mandible is stationary
and the teeth from both upper and lower arches
approximate.
THE CHEWING CYCLE
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11. Muscles of mastication- originate skull & insert mandible
Only mandible moves during mastication and other activities
Four muscles are the primary participants in mastication, other
accessory muscles.
Each of these primary muscles of mastication is paired
THE CHEWING CYCLE
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12. They are:
1. Masseter
2. Temporalis
3. Lateral pterygoid
4. Medial pterygoid
Develop from the mesoderm of the 1st brachial arch.
Supplied by the mandibular nerve.
PRIMARY MUSCLES OF
MASTICATION
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13.  Quadrilateral
 Covers lateral surface of ramus
of mandible.
Three layers
 1. superficial layer
[largest]
 2. middle layer
 3. deep layer
MASSETER
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MASSETER

14. 1.SUPERFICIAL LAYER
ORIGIN:
Maxillary process of the
zygomatic bone and anterior
2/3rd of lower border of
zygomatic arch.
 FIBRES:
Passes downwards &
backwards at 45 degrees.
MASSETER
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15. INSERTION: Lower part of the lateral surface of the
ramus of mandible.
MASSETER
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16. 2. MIDDLE LAYER :
ORIGIN :
Medial aspect of 2/3rd of
zygomatic bone & posterior 1/3rd
of lower border of zygomatic arch.
FIBRES :
Passes vertically downwards.
INSERTION :
Upper part of ramus of the
mandible.
MASSETER
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17. 3. DEEP LAYER :
 ORIGIN:
Deep surface of zygomatic
arch.
 FIBRES:
Passes vertically downwards.
 INSERTION:
Upper part of ramus &
coronoid process of mandible.
MASSETER
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18. NERVE SUPPLY:
Masseteric nerve, a branch of anterior division of
mandibular nerve.
ACTIONS:
1. Elevates mandible to occlude teeth in mastication.
2. Small effect in side-to-side movements, protraction &
retraction.
MASSETER
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19. SUPERFICIAL:
skin
Platysma
risorius
zygomaticus major
parotid gland
Muscle is crossed by
parotid duct branches of
facial nerve transverse facial
vessels
MASSETER
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20. DEEP:
Temporalis – lower part
mandibular ramus
Masseteric nerve & artery
A mass of fat seperates it in
front from buccinator &
buccal nerve
POSTERIOR MARGIN:
Overlapped by parotid gland
ANTERIOR MARGIN:
Projects over buccinator & is
crossed by facial nerve
MASSETER
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21. Dissected muscle consist of 6 alternating musculo-aponuerotic
layers, which is divided into 3 planes
Anterior and posterior fan contains 3-3 musculo-aponuerotic
layers
Superficial/prior- 60* angulation with Frankfort horizontal plane
Deep/alter lamina- 60* angulation with Frankfort horizontal
plane
Intermediate- 90* angulation with Frankfort horizontal plane
MASSETER
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22. Fan shaped muscle, fills the
temporal fossa.
ORIGIN:
Whole of the temporal fossa
except the part formed by
zygomatic bone.
Deep surface of temporal fascia.
TEMPORALIS
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23. FIBRES:
Converge & descends into a
tendon which passes through
the gap between zygomatic arch
& side of skull.
Anterior fibers -- oriented
vertically.
Posterior fibers – horizontally.
Intermediate fibers -- obliquely
TEMPORALIS
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24. INSERTION:
Margins & deep surface of
coronoid process,
Anterior border of the ramus
of mandible almost to last
molar.
NERVE SUPPLY:
Two deep temporal branches
from anterior division of
mandibular nerve.
TEMPORALIS
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25. SUPERFICIAL :
Skin
Auricularis anterior & superior
Temporal fascia
Superior temporal vessels
Auriculo temporal nerve
Temporal branches of facial nerve
Zygomatico temporal nerve
Epicranial aponeurosis
Zygomatic arch
Masseter.
RELATIONS
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26. DEEP:
Temporal fossa
Lateral pterygoid
Superficial head of medial
pterygoid
A small part of buccinator
Maxillary artery & its deep
temporal branches
Deep temporal nerves
Buccal nerve & vessels
Anterior border is separated
from the zygomatic bone by a
mass of fat.
RELATIONS
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27. Elevates the mandible to close the mouth & approximate
the teeth.
The movement requires both the upward pull of the anterior
fibers & backward pull of the posterior fibers.
Contributes to side- to- side grinding movements.
Posterior fibers retracts the mandible.
Vitti & Basmajian (1977) suggests that the temporalis is
active in forcible elevation, but not in slow elevation with
out occlusion.
ACTIONS
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28. LATERAL PTERYGOID
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 Short, conical, thick muscle with two heads.

29. ORIGIN:
UPPER HEAD:
Infra temporal surface &
infra temporal crest of the
greater wing of sphenoid
bone.
LOWER HEAD:
Lateral surface of lateral
pterygoid plate.
NERVE SUPPLY:
A branch from anterior
division of mandibular nerve.
LATERAL PTERYGOID
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30. LATERAL PTERYGOID
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31. FIBRES:
Passes backwards & laterally,
and converge to insert.
INSERTION:
Pterygoid fovea of the
mandible,
articular disc,
Capsule of the T.M.J.
Insertion is postero lateral & at
a slightly higher level than
origin.
LATERAL PTERYGOID
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32. Early 3rd mth I.U, muscle inserts into mesenchyme that
condenses around developing condyle, but, part of it’s
tendon sweeps backward above the condyle & gets
inserted into the portion of Meckel’s cartilage that later
forms the head of the malleus.
-Harpman & Woollard (1938).
This part of tendon become inserted into the articular disc
of T.M.J & it’s attachment to the malleus does not
persists.
- Rees (1954)
LATERAL PTERYGOID
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33. Opening the mouth – by pulling forward the condylar
process of mandible & articular disc, while head of the
mandible rotates on the articular disc.
During closure of mouth, the backward gliding of the
articular disc & condyle is controlled by slow elevation
of lateral pterygoid, while the masseter & temporalis
restore the jaw to the occlusal position.
- Posselt (1952).
ACTIONS
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34. 2. Left lateral pterygoid & right medial pterygoid
turn the chin to left side as a part of grinding
movements.
3. Medial & lateral pterygoids of two sides act
together & protrude mandible, so that the lower
incisors projects infront of the upper.
Upper head is involved mainly in chewing.
Lower head is in protrusion.
ACTIONS
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35. Relations
LATERALPTERYGOID
REATIONS
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Body_ID: HC030020
The mandibular ramus and masseter, the maxillary artery - which crosses
either deep or superficial to the muscle
Superficially - superficial head of medial pterygoid and the tendon of
temporalis.
Deep - deep head of medial pterygoid, the sphenomandibular ligament,
middle meningeal artery,
mandibular nerve.
Upper border - temporal and masseteric branches of the mandibular nerve.
Lower border -lingual and inferior alveolar nerves.
The buccal nerve and the maxillary artery pass between the two heads of the
muscles

36. ORIGIN:
SUPERFICIAL HEAD (SMALL SLIP)
Lateral surface of the pyramidal
process & maxillary tuberosity.
DEEP HEAD (QUITE LARGE)
Medial surface of the lateral
pterygoid plate & the grooved surface
of the pyramidal process of the
palatine bone.
FIBRES:
Runs downwards, backwards &
laterally.
MEDIALPTERYGOID
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37. Attached by a strong tendinous
lamina to the postero inferior
part of the medial surface of
the mandibular ramus & angle,
as high as mandibular
foramina & almost as forward
as the mylohyoid groove.
NERVE SUPPLY:
A branch from the mandibular
nerve.
INSERTION
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38. MEDIAL PTERYGOID
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39. SUPERFICIAL:
Separated from lateral pterygoid
muscle & ramus of mandible by
lateral pterygoid plate,
maxillary artery,
Inferior alveolar vessels &
nerves,
Lingual nerve,
Spheno mandibular ligament.
Process of the parotid gland
separated from masseter by
lower part of the ramus of
mandible
RELATIONS
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40. Elevates the mandible.
Acting with lateral pterygoid, it protrudes the mandible.
When the medial & lateral pterygoid’s of one side act
together, the corresponding side of mandible is rotated
forwards to the opposite side, with the opposite
mandibular head as a vertical axis.
Alternating activity in the left & right sets of muscles
produces side-to-side movements, which are used to
triturate food.
ACTIONS
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41. In 1996, researchers at the UNVERSITY OF MARYLAND
identified a new muscle in the skull and named it
SPHENOMANDIBULARIS.
ORIGIN AND INSERTION:
It extends from the lateral surface of the sphenoid bone to the
medial surface of the coronoid process and ramus of the
mandible.
The muscle is believed to be either a fifth muscle of mastication
or a previously unidentified component of an already identified
muscle.
NERVE SUPPLY: It is supplied by the maxillary branch of
trigeminal nerve.
THE FIFTH MUSCLE OF MASTICATION
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42. They are paired muscles.
Anterior digastric
Mylohyoid
Geniohyoid
Buccinator
ACCESSORY MUSCLES OF MASTICATION
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43. Two bellies united by an intermediate
tendon
ORIGIN :
Anterior belly – Digastric fossa of
mandible
Posterior belly - mastoid notch on the
medial side of the base of the mastoid
process
FIBRES :
Anterior belly runs downwards &
backwards
Posterior belly runs downwards &
forwards
INSERTION :
Both the heads meet at the intermediate
tendon which perforates stylohyoid
muscle & is held by a fibrous pulley to
the hyoid bone.
DIGASTRIC MUSCLE
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44. NERVE SUPPLY :
ANTERIOR BELLY:
Mylohyoid nerve, a branch of the
mandibular division of trigeminal nerve
POSTERIO BELLY:
Nerve from posterior auricular branch of
facial nerve
ACTIONS :
Depress and retract the mandible, so
assisting the lateral pterygoid muscle in
opening the mouth
elevation of the hyoid bone, utilized during
swallowing and speech
DIGASTRICMUSCLE
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45. RELATIONS –
Superficial -platysma,
sternocleidomastoid,
splenius capitis, longissimus capitis,
stylohyoid, mastoid process,
the retromandibular vein,
the parotid and submandibular salivary glands.
DIGASTRICMUSCLE
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46. RELATIONS –
DIGASTRICMUSCLE
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Medial to the anterior belly-
Mylohyoid, hyoglossus,
superior oblique,
rectus capitis lateralis,
the transverse process of the atlas vertebra,
internal jugular vein,
occipital artery,
hypoglossal nerve,
internal and external carotid, facial and lingual arteries- medial to posterior belly

47. Flat, triangular muscle.
Two mylohyoids forms floor of mouth
Situated just below the anterior belly of
digastric muscle
ORIGIN :
Mylohyoid line of mandible, extends
from symphysis in front to last molar
tooth behind
INSERTION :
Posterior fibres :Body of hyoid bone
Middle & anterior fibres : median raphe
between mandible &hyoid bone
MYLOHYOID
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48. Fibres Runs medially & slightly downwards
NERVE SUPPLY :
Mylohyoid nerve, a nerve from mandibular division of the
trigeminal nerve
ACTION :
Elevates floor of mouth in deglutition
Depress the mandible & elevates hyoid bone
MYLOHYOID
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49. The inferior (external) surface –
platysma,
anterior belly of digastric,
the superficial part of the
submandibular gland,
the facial and submental vessels,
and the mylohyoid vessels and nerve.
posteriorly-
the mucous membrane of the mouth.
MYLOHYOID
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The superior (internal) surface-
geniohyoid,
part of hyoglossus and styloglossus,
the hypoglossal and lingual nerves,
the submandibular ganglion,
the sublingual gland,
the deep part of the submandibular
gland and its duct,
the lingual and sublingual vessels

50. Thin quadrilateral muscle
ORIGIN :
Upper fibres, from maxilla, opposite molar
teeth
Lower fibres, from mandible, opposite molar
teeth
Middle fibres, from pterygomandibular raphe
INSERTION :
Upper fibres – Upper lip
Lower fibres – Lower lip
Middle fibres – Decussate before passing to
lips
ACTION :
Flattens cheek against gums & teeth
Prevents accumulation of food in the
vestibule.
BUCCINATOR
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51. Anteriorly –
the superficial surface of buccinator is related to zygomaticus major,
risorius, levator and depressor anguli oris, and the parotid duct. It is
crossed by the facial artery, facial vein and branches of the facial and
buccal nerves.
Posteriorly –
buccinator lies in the same plane as the superior pharyngeal
constrictor, which arises from the posterior margin of the
pterygomandibular raphe, and is covered there by the buccopharyngeal
fascia.
BUCCINATOR
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52. Superficially –
the buccal pad of fat separates the posterior part of buccinator from
the ramus of the mandible, masseter and part of temporalis.
Deep surface –
the buccal glands and mucous membrane of the mouth. The parotid
duct pierces buccinator opposite the third upper molar tooth, and lies
on the deep surface of the muscle before opening into the mouth
opposite the maxillary second molar tooth
BUCCINATOR
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53. Short & narrow muscle
Lies above medial part of
mylohyoid muscle
ORIGIN :
Inferior mental spine
FIBRES :
Runs backwards & downwards
GENIOHYOID
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54. INSERTION :
Anterior surface of body of hyoid bone
NERVE SUPPLY :
By fibres from 1st cervical nerve via
hypoglossal nerve
ACTION :
Elevates hyoid bone
Depress mandible
GENIOHYOID
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55. MUSCLES RESPONSIBLE FOR MOVEMENTS OF
MANDIBLE
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56. PALPATION

58. The anterior region is palpated above the zygomatic arch and anterior to
the TMJ
The middle region is palpated directly above the TMJ and superior to
the zygomatic arch
The posterior region is palpated above and behind the ear

59. Masseter Muscle

60. 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 clench during 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

61. LATERAL PTERYGOID
Placing the forefinger, or the
little finger, over the buccal area
of the maxillary third molar
region and exerting pressure in a
posterior, superior, and medial
direction behind the maxillary
tuberosity

62. PALPATION OF
MEDIAL PTERYGOID

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

64. In case of uni or bilateral condylar fractures due to the pull
of lateral pterygoid, the fractured condylar heads displaces
anteromedially, thus reducing the height of the ramus of
mandible, there by causing posterior gag & anterior open
bite.
APPLIED ASPECTS
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65. In case of unfavorable angle fractures, medial
pterygoid & masseter pulls the fragment upwards
causing difficulty in fracture reduction.
APPLIEDASPECTS
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66. In case of bilateral para symphysis fractures, due to the pull
of digastric, geniohyoid & genioglossus, the fractured
segment is pulled posteriorly & inferiorly, there by
causing fall back of tongue and compromising the airway.
This usually happens in unconscious patients.
APPLIEDASPECTS
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67. Beginning at about 30 Years of age these is a progressive
loss of skeletal muscle mass that is largely replaced by fat.
Due to loss of muscle mass, there is a decrease in maximal
strength and a diminishing of muscle reflexes
Muscle spasm of the masseter and lateral pterygoid
associated with excessively wide opening of mouth results
in lock jaw in dislocated position.
AGEING
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68. A lesion at foramen ovale results in parenthesis along the
mandible, the mandibular teeth and the side of face, as well of
paralysis of muscles of mastication.
An injury to nerve supply to muscles of mastication causes the
chin to be drawn to the paralyzed side on protraction. This is due
to lack of contraction of medial and lateral pterygoid muscle on
paralyzed side.
APPLIEDANATOMY
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69. Acute inflammation of masseter muscle with pain, swelling,
tenderness restriction. This may be caused due to cellulitis,
trauma, and irritation of the muscle.
This can be treated by anti inflammatory analgesics, gentle range
of motion exercise.
MYOSITIS
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70. Inflammatory lesions about the mandibular joint
may produce a chronic masseter myositis with
subsequent fibrosis which may restrict the play of
muscles & limit the movements of the jaw.
APPLIEDASPECTS
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71. Intensive bruxism of long duration, may result in
masseter muscle hypertrophy. This may cause muscle pain, tender
on palpation. It may also be associated with temporalis muscle
hypertrophy.
MASSETER HYPERTROPHY
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72. MYASTHENIA GRAVIS
Acquired autoimmune disorder of neuromuscular transmission characterized by
muscle weakness
ETIOLOGY
Antibodies to acetylcholine receptor on skeletal muscle fiber
CLINICAL FEATURES
Diplopia, ptosis, drooping of the face, And a very sorrowful appearance to the
patient.
Patient rapidly exhausted, lose weight, death frequently occurs from respiratory
failure.

73. TREATMENT AND
PROGNOSIS
Physostigmine administered intramuscularly improves the
strength of the affected muscle in a matter of minutes
No cure is known even though the prognosis is good in the
relapsing type.

74. 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
Risus sardonicus
Opisthotonous

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

76. 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

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

78. MYOPATHIES
Myopathy is a neuromuscular disease in which the dysfunction of muscle fibers
leads to muscular weakness.
The diseases may or may not involve the nervous system.
The common diseases are:-
1 -Muscular dystrophy
 Duchenne muscular dystrophy
 Backers muscular dystrophy

79. 2 – Diseases involving muscle tone
 Hypertonia
 Hypotonia
 Myotonia
3 – Fibrillation and denervation hypersensitivity
4 – Myasthenia gravis
5 – Lambert-Eaton syndrome
6 – McARDLES syndrome
7 – Mitochondrial hypopathy
8 – Nemaline myopathy

80. MUSCLE HYPERTROPHY, ATROPHY,
HYPERPLASIA
HYPERTROPHY: when total mass of muscle enlarges.,
increase in actin and myosin filament in response to
maximal force causing enlargement of muscle fiber.
HYPERPLASIA: Under rare condition of extreme muscle
force generation actual number of muscle fiber have been
observed to increase.
ATROPHY: When total mass of muscle decreases.

81. TRISMUS

82. CAUSES
Pericoronitis
Masticatory space infection
Inferior alveolar nerve block
Post surgical trismus
Tetanus
Hypocalcemic tetani

83. MASTICATORY SPACE
INFECTIONS

84. SUB MASSETERIC
SPACE INFECTION

85. PTERYGOMANDIBULAR
SPACE INFECTION

86. MYOFACIAL PAIN
DYSFUNCTION SYNDROME

87. MPDS
Defined as – pain is constant, dull in nature, in contrast to the sudden sharp,
shooting, intermittent pain of neuralgia [chronic pain ]. But the pain may
range from mild to intolerable.
The condition is ch/by unilateral facial pain secondary to the TMJ disorder,
which is often associated with periarticular muscle spasm and pain with
dysfunction of the spastic muscle

88. ETIOLOGICAL FACTORS
The factors are:-
1- Intra-capsular causes:
Internal derangements like-
I. Anterior disc dislocation with reduction and without reduction
II. Disc perforation
III. Disc adhesions

89. 2 Extra-capsular causes-
Occlusal disharmony
Psychosis
Muscular imbalance
Hypermobility, subluxation
Muscular over extension due to restoration or prosthesis
Muscle overecontraction- loss of posterior teeth
Para-functions- bruxism, clenching, grinding etc

90. CLINICAL FEATURE
Pain which is usually unilateral and aggravated on chewing, yawning , and
opening.
Pain in temples, vertex, occipital areas, headaches, neck and shoulder aches are
common.
Restricted joint excursion
Pathological joint sounds – clicking sound, crepitus like sound.
Muscle tenderness.
Otological symptoms.
Occlusal discrepancies.
Altered psychosis.
Subluxation or dislocation

91. MANAGEMENT
1 Pharmacologicle T/t.
2 Intra- articular injection.
3 Occlusal splints.
4 physiotherapeutic T/t.
5 stress management.
6 Biofeedback and relaxation therapy.
7 Psychological T/t.
8 surgical T/t:- a] Arthrocentesis

92. B] capsule tightening procedures .
C] creating mechanical obstacle.
D] removal of mechanical obstacle.
F] creation of new muscle balance .

93. 1. Gray’s Anatomy
- Churchill Livingstone.
2. Human anatomy
- B. D. Chaurasia.
3. Grant’s Atlas of Anatomy
- Anne M. R. Agur , Arthur F.Dalley.
4. Text book of Anatomy with Colour Atlas
- Inderbir Singh.
5. Oral and Maxillofacial Trauma
- Fonseca.
6. Text book of Histology
- Hiatt & Garner
7. Text Book of Medical Physiology
- Arthur C. Guyton
REFERENCES
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94. THANK YOU
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