2 muscles of mastication rt(76) Dr. RAHUL TIWARI

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R T 2 / M U S C L E S O F M A S T I C A T I O N / 7 6

GOOD AFTERNOON

MUSCLES OF MASTICATION

PRESENTED BYDr. RAHUL TIWARI

1ST YEAR MDS - PG StudentDEPT. OF ORAL & MAXILLOFACIAL SURGERY

SIBAR INSTITUTE OF DENTAL SCIENCES

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INTRODUCTIONEMBRYOLOGYHISTOLOGY

MUSCLES OF MASTICATIONMASSETER

TEMPORALISMEDIAL PTERYGOIDLATERAL PTERYGOID

ACCESSORY MUSCLES OF MASTICATIONAPPLIED ASPECTS

CONCLUSIONREFERENCES

CONTENTS

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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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A tissue specialized to produce motion in response to muscle action potentials by its

qualities of contractility, extensibility elasticity and excitability.

These tissues bring about voluntary and involuntary movement of parts of the body.

The main functions of muscles are- Motion (Both reflex and voluntary), Maintenance of Posture, Heat production

MUSCLE TISSUE

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At the birth suckling muscles of the lips and cheeks are relatively better developed than the muscles of mastication.

But between the birth and adulthood the facial muscles increase fourfold and MOM sevenfold in weight.

The masseter and medial pterygoid are better developed than temporalis and lateral pterygoid.

MASTICATORY MUSCLES

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MYOGENESIS

MRF- MyoD1, MRF5,

MRF-4/herculin/MYF-6 and myogenin

MYOFIBRES from the paraxial

mesoderm with contractile properties

unsegmented head mesoderm and segmented

(somitic) mesoderm.

pharyngeal-arch muscles.

EMBRYOLOGY

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EMBRYOLOGY

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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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MYOMERES & MYOTOMES

MYOBLASTS

MYOTUBES

EMBRYOLOGY

MYOCYTES

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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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FOURTH SOMITOMERE

THE FIRST PHARYNGEAL

ARCH

FOUR MUSCLES OF

MASTICATION

TRIGEMINAL (FIFTH

CRANIAL) NERVE.

EMBRYOLOGY

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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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HISTOLOGY

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Skeletal-Elongated and tubular, multiple nuclei located in

periphery.Striated muscle has alternating light and dark

bandsCardiac-

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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ANATOMY

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CONTRACTION

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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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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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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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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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Quadrilateral Covers lateral surface of

ramus of mandible.

Three layers 1. superficial layer

[largest] 2. middle layer 3. deep layer

MASSETER

MASSETER

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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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INSERTION: Lower part of the lateral surface of the ramus of mandible.

MASSETER

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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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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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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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SUPERFICIAL:

skinPlatysmarisoriuszygomaticus majorparotid gland

Muscle is crossed byparotid duct branches of facial nerve transverse facial vessels

MASSETER

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DEEP:Temporalis – lower part

mandibular ramusMasseteric 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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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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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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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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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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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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DEEP:Temporal fossaLateral pterygoidSuperficial head of

medial pterygoidA small part of

buccinatorMaxillary artery & its

deep temporal branches

Deep temporal nervesBuccal nerve & vesselsAnterior border is

separated from the zygomatic bone by a mass of fat.

RELATIONS

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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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LATERAL PTERYGOID

Short, conical, thick muscle with two heads.

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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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LATERAL PTERYGOID

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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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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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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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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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Relations

LATERAL PTERYGOIDREATIONS

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

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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.

MEDIAL PTERYGOID

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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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MEDIAL PTERYGOID

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SUPERFICIAL:

Separated from lateral pterygoid muscle & ramus of

mandible bylateral 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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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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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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They are paired muscles.

Anterior digastric

Mylohyoid

Geniohyoid

Buccinator

ACCESSORY MUSCLES OF MASTICATION

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Two bellies united by an intermediate tendon

ORIGIN :Anterior belly – Digastric fossa

of mandiblePosterior belly - mastoid notch on the medial side of the base

of the mastoid processFIBRES :

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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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

DIGASTRIC MUSCLE

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RELATIONS –

Superficial -platysma,

sternocleidomastoid,

splenius capitis, longissimus capitis,

stylohyoid, mastoid process,

the retromandibular vein,

the parotid and submandibular salivary glands.

DIGASTRIC MUSCLE

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RELATIONS –

DIGASTRIC MUSCLE

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

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Flat, triangular muscle.Two mylohyoids forms floor of

mouthSituated 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

boneMiddle & anterior fibres : median

raphe between mandible &hyoid bone

MYLOHYOID

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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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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

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

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Thin quadrilateral muscleORIGIN :

Upper fibres, from maxilla, opposite molar teeth

Lower fibres, from mandible, opposite molar teethMiddle fibres, from

pterygomandibular rapheINSERTION :

Upper fibres – Upper lipLower fibres – Lower lip

Middle fibres – Decussate before passing to lips

ACTION :Flattens cheek against gums &

teethPrevents accumulation of food in

the vestibule.

BUCCINATOR

http://en.wikipedia.org/wiki/Image:Buccinator.jpg

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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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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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Short & narrow muscle

Lies above medial part of mylohyoid muscle

ORIGIN :

Inferior mental spine

FIBRES : Runs backwards & downwards

GENIOHYOID

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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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MUSCLES RESPONSIBLE FOR MOVEMENTS OF MANDIBLE

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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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In case of unfavorable angle fractures, medial pterygoid & masseter pulls the fragment upwards causing difficulty

in fracture reduction.

APPLIED ASPECTS

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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.

APPLIED ASPECTS

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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.

APPLIED ASPECTS

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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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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.

APPLIED ANATOMY

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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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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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Is an autoimmune disorder, results in abnormality at the

neuromuscular junction, resulting in prevention of muscle fiber

contraction which in turn causes weakness of skeletal muscle.

MYASTHENIA GRAVIS

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Limitation of jaw opening due to spasm of mastication

muscles is a rare complication of mandibular

anesthesia.

There is decrease in jaw opening 2-4 days and no

associated pain.

It takes 2-4 weeks to recover.

TRISMUS AFTER INJECTION

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JUST AS THE CLINICIAN NEEDS THE MEDICAL

HISTORY TO MAKE A LOGICAL DIAGNOSIS,

SO TO THE ANATOMY OF MUSCLE IS ESSENTIAL

FOR A LOGICAL EXPLANATION OF ANY

STRUCTURAL AND FUNCTIONAL IMBALANCES IF

IT DO OCCURS

CONCLUSION

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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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THANK YOU FOR YOUR KIND ATTENTION

AND ACTIVE PARTICIPATION

FOR YOUR BRIGTHER TOMORROW

SAVE ELECTRICITY TODAY

2 muscles of mastication rt(76) Dr. RAHUL TIWARI

Health & Medicine

Transcript of 2 muscles of mastication rt(76) Dr. RAHUL TIWARI