Muscles of mastication/prosthodontic courses

MUSCLES
OF
MASTICATION
www.indiandentalacademy.com

ContentsContents
IntroductionIntroduction
Primary Muscles Of MasticationPrimary Muscles Of Mastication
Accessory Muscles Of MasticationAccessory Muscles Of Mastication
Development Of Muscles Of MasticationDevelopment Of Muscles Of Mastication
Function Of MusclesFunction Of Muscles
Applied AnatomyApplied Anatomy
Disorders Of MusclesDisorders Of Muscles
ConclusionConclusion
ReferencesReferences

INTRODUCTIONINTRODUCTION
 Skeletal components of body are heldSkeletal components of body are held
together and moved by skeletaltogether and moved by skeletal
muscles.muscles.
 The attachment of the muscle to theThe attachment of the muscle to the
fixed part is known asfixed part is known as originorigin andand
attachment to the movable part isattachment to the movable part is
insertioninsertion..

PRIMARY MUSCLES OFPRIMARY MUSCLES OF
MASTICATIONMASTICATION
 The muscles of mastication are of two typesThe muscles of mastication are of two types
 PrimaryPrimary
 AccessoryAccessory
PRIMARY MUSCLESPRIMARY MUSCLES
 MasseterMasseter
 TemporalisTemporalis
 Lateral PterygoidLateral Pterygoid
 Medial PterygoidMedial Pterygoid

MasseterMasseter
 Greek word “Greek word “masetermaseter”- a”- a
chewerchewer
 This is aThis is a quadrilateralquadrilateral
muscle which covers themuscle which covers the
lateral part of ramus oflateral part of ramus of
mandible.mandible.
 It consists ofIt consists of 3 layers3 layers
which blend anteriorly.which blend anteriorly.

OriginOrigin
 Superficial layerSuperficial layer
(largest)(largest)
 maxillary processmaxillary process ofof
zygomatic bonezygomatic bone
 anterior 2/3anterior 2/3rdrd
ofof inferiorinferior
borderborder of zygomatic archof zygomatic arch
 Middle layerMiddle layer
 medial aspectmedial aspect of anteriorof anterior
2/32/3rdrd
of zygomatic archof zygomatic arch
 lower borderlower border of posteriorof posterior
third of zygomatic archthird of zygomatic arch
 Deep layerDeep layer ––
 arises from thearises from the deepdeep
surfacesurface of zygomatic arch.of zygomatic arch.

InsertionInsertion
 Superficial layerSuperficial layer
 AngleAngle of mandibleof mandible
 Lower posterior halfLower posterior half ofof
lateral surface oflateral surface of
mandibular ramus.mandibular ramus.
 Middle layerMiddle layer
 central partcentral part of mandibularof mandibular
ramus.ramus.
 Deep layerDeep layer
 upper partupper part of mandibularof mandibular
ramusramus
 coronoidcoronoid process.process.

MasseterMasseter
 Nerve supplyNerve supply
 Supplied bySupplied by masseteric nervemasseteric nerve aa
branch of anterior division ofbranch of anterior division of
mandibular nervemandibular nerve
 Blood supplyBlood supply
 Supplied bySupplied by masseteric arterymasseteric artery
branch of maxillary arterybranch of maxillary artery
 Venous drainage throughVenous drainage through
masseteric veinmasseteric vein
 ActionAction
 The muscleThe muscle elevateselevates thethe
mandible to close the mouth,mandible to close the mouth,
and clenches the teethand clenches the teeth

TemporalisTemporalis
It is a powerful fan shapedIt is a powerful fan shaped
chewing muscle whichchewing muscle which
fills temporal fossafills temporal fossa
 OriginOrigin
 Temporal fossa fromTemporal fossa from
infatemporal - linesinfatemporal - lines
excludingexcluding
 zygomatic bonezygomatic bone
 Temporal fasciaTemporal fascia
 InsertionInsertion
 Margins & deep surfaceMargins & deep surface ofof
the coronoid processthe coronoid process
 Anterior borderAnterior border of ramus ofof ramus of
mandiblemandible

TEMPORALISTEMPORALIS
 Deep temporal branchesDeep temporal branches fromfrom
anterior division of mandibularanterior division of mandibular
nervenerve
 Superficial temporal arterySuperficial temporal artery branchbranch
of maxillary arteryof maxillary artery
 superficial temporal veinsuperficial temporal vein & middle& middle
temporal veintemporal vein
 ActionAction
 ElevatesElevates the mandiblethe mandible
 posterior fibersposterior fibers retractretract thethe
protruded mandibleprotruded mandible
 Applied anatomyApplied anatomy
 Sudden reflex contraction ofSudden reflex contraction of
temporalis in times of trauma cantemporalis in times of trauma can
cause thecause the fracturefracture of coronoidof coronoid
processprocess www.indiandentalacademy.com

Lateral pterygoidLateral pterygoid
 It is a short thick conical muscle with definite upper and lower headsIt is a short thick conical muscle with definite upper and lower heads
 OriginOrigin
 Upper head arises fromUpper head arises from infra temporal surfaceinfra temporal surface and crest ofand crest of greater wing ofgreater wing of
sphenoid bonesphenoid bone
 Lower head from theLower head from the lateral pterygoid platelateral pterygoid plate
 Fibers run backwards and laterally and converge into theFibers run backwards and laterally and converge into the pterygoid foveapterygoid fovea
on anterior surface of neck of mandibleon anterior surface of neck of mandible
 Into anterior margin ofInto anterior margin of articular discarticular disc andand capsulecapsule of TMJof TMJ

Lateral pterygoidLateral pterygoid
 A branch from anterior divisionA branch from anterior division
of theof the mandibular nervemandibular nerve
 Maxillary arteryMaxillary artery
 Ascending palatine arteryAscending palatine artery
 ActionAction
 DepressesDepresses the mandible tothe mandible to
open mouthopen mouth
 Lat. & Medial pterygoid of bothLat. & Medial pterygoid of both
sides contract tosides contract to protrudeprotrude thethe
mandiblemandible
 when contract alternativelywhen contract alternatively
producesproduces chewing movementschewing movements

Medial pterygoidMedial pterygoid
This isThis is quadrilateral musclequadrilateral muscle
having a smallhaving a small superficialsuperficial headhead
and a largeand a large deepdeep head whichhead which
forms the major part of muscleforms the major part of muscle
 OriginOrigin
 Superficial head fromSuperficial head from maxillarymaxillary
tuberositytuberosity
 Deep head from medial surface ofDeep head from medial surface of
lateral pterygoid platelateral pterygoid plate and part ofand part of
palatine bonepalatine bone
 Fibers run backwards, downwardsFibers run backwards, downwards
and laterally into the roughenedand laterally into the roughened
area ofarea of medial surface of the anglemedial surface of the angle
mandiblemandible

Medial pterygoidMedial pterygoid
 Branch of theBranch of the main trunkmain trunk ofof
mandibular nervemandibular nerve
 By facial arteryBy facial artery
 lingual veinlingual vein
 ActionAction
 ElevatesElevates andand protrudesprotrudes thethe
mandiblemandible
 Applied anatomyApplied anatomy
 During improper inferiorDuring improper inferior
alveolar nerve block, thealveolar nerve block, the
needle may prick & irritate theneedle may prick & irritate the
muscle causing spasm &muscle causing spasm &
consequently trismusconsequently trismus

RelationsRelations
Lateral PterygoidLateral Pterygoid
 Superficial:-Superficial:-
 MasseterMasseter
 Ramus of mandibleRamus of mandible
 Tendon of temporalisTendon of temporalis
 Deep:-Deep:-
 Mandibular nerveMandibular nerve
 Middle Meningeal arteryMiddle Meningeal artery
 SphenomandibularSphenomandibular
ligamentligament
 Deep head of medialDeep head of medial
pterygoidpterygoid
 Structures emerging at upperStructures emerging at upper
border:-border:-
 Deep temporal nerveDeep temporal nerve
 Masseteric nerveMasseteric nerve
 Structures emerging at lowerStructures emerging at lower
border:-border:-
 Lingual nerveLingual nerve
 Inferior alveolar nerveInferior alveolar nerve
 Middle meningeal arteryMiddle meningeal artery
passes upwards deep to itpasses upwards deep to it
 Structures passing throughStructures passing through
gap between two heads:-gap between two heads:-
 Maxillary artery entersMaxillary artery enters
the gapthe gap
 Buccal branch ofBuccal branch of
mandibular nerve comesmandibular nerve comes
out of that gapout of that gapwww.indiandentalacademy.com

RelationsRelations
Medial PterygoidMedial Pterygoid
Superficial relations:-Superficial relations:-
 Upper part of muscle is separated from Lateral Pterygoid by:-Upper part of muscle is separated from Lateral Pterygoid by:-
 Lateral pterygoid plateLateral pterygoid plate
 Lower part of muscle is separated from Lateral Pterygoid by:-Lower part of muscle is separated from Lateral Pterygoid by:-
 Mandibular ramusMandibular ramus
 Sphenomandibular ligamentSphenomandibular ligament
Deep relationsDeep relations
 Tensor veli palatiniTensor veli palatini
 Superior constrictor of pharynxSuperior constrictor of pharynx
 StyloglossusStyloglossus
 Stylopharyngeus attached to styloid processStylopharyngeus attached to styloid process

ACCESSORY MUSCLES OFACCESSORY MUSCLES OF
MASTICATIONMASTICATION
 DIGASTRICDIGASTRIC
 MYLOHYOIDMYLOHYOID
 GENIOHYOIDGENIOHYOID
 PLATYSMAPLATYSMA
 BUCCINATORBUCCINATOR

Digastric muscleDigastric muscle
 This muscle has 2 bellies anterior & posteriorThis muscle has 2 bellies anterior & posterior
 OriginOrigin
 Anterior belly originates fromAnterior belly originates from Digastric fossaDigastric fossa at inner side of lowerat inner side of lower
border of mandibleborder of mandible
 Anterior belly descend to hyoid bone & joinAnterior belly descend to hyoid bone & join intermediate tendonintermediate tendon whichwhich
is connected to hyoid bone by fibrous tissue called Digastric pulleyis connected to hyoid bone by fibrous tissue called Digastric pulley
 ByBy Mylohyoid nerveMylohyoid nerve branch of inferior alveolar nerve which is a branchbranch of inferior alveolar nerve which is a branch
of mandibular nerveof mandibular nerve
 ByBy lingual artery & veinlingual artery & vein
 ActionAction
 Depresses the mandible and mostly acts in maximal depressionDepresses the mandible and mostly acts in maximal depression

Mylohyoid muscleMylohyoid muscle
This muscle forms the floor of the mouthThis muscle forms the floor of the mouth
 OriginOrigin
 Whole length ofWhole length of Mylohyoid line to the 3Mylohyoid line to the 3rdrd
molarmolar of inside ofof inside of
mandiblemandible
 Fibers pass down & some are inserted intoFibers pass down & some are inserted into median raphaemedian raphae & rest& rest
into theinto the hyoid bonehyoid bone
 ByBy Mylohyoid nervesMylohyoid nerves branch of inferior alveolar nervebranch of inferior alveolar nerve
 ActionAction
 Elevation of the floor of mouth in the 1Elevation of the floor of mouth in the 1stst
stage of deglutitionstage of deglutition
 Elevates hyoid bone or depresses the mandibleElevates hyoid bone or depresses the mandible

Geniohyoid muscleGeniohyoid muscle
This is a narrow muscle lying above the medial part ofThis is a narrow muscle lying above the medial part of
MylohyoidMylohyoid
 OriginOrigin
 From theFrom the genial tuberclegenial tubercle of symphysisof symphysis
 At anterior surface of body ofAt anterior surface of body of hyoid bonehyoid bone
 Supplied by theSupplied by the hypoglossal nervehypoglossal nerve
 ActionAction
 Depresses mandible when hyoid is fixedDepresses mandible when hyoid is fixed

PlatysmaPlatysma
This is a large thin muscleThis is a large thin muscle
 OriginOrigin
 Upper parts ofUpper parts of pectoral and deltoid fasciaepectoral and deltoid fasciae
 Anterior fibersAnterior fibers –base of mandible–base of mandible
 Posterior fibersPosterior fibers –skin of lower face and lip–skin of lower face and lip
 cervical branch ofcervical branch of Facial nerveFacial nerve
 ActionAction
 DepressesDepresses the lower jaw and lipthe lower jaw and lip

BuccinatorBuccinator
 Origin:-Origin:-
 Upper fibers –Upper fibers – maxilla opposite molarsmaxilla opposite molars
 Lower fibers –Lower fibers – mandible opposite molar teethmandible opposite molar teeth
 Middle fibersMiddle fibers – pterygomandibular raphae– pterygomandibular raphae
 Insertion :-Insertion :-
 Upper fibersUpper fibers – straight to upper lip– straight to upper lip
 Lower fibersLower fibers – straight to lower lip– straight to lower lip
 Middle fibersMiddle fibers – decussate before passing to the lip– decussate before passing to the lip
 Nerve supply –Nerve supply –
 lower buccal branch oflower buccal branch of facial nervefacial nerve
 Actions –Actions –
 flattens cheekflattens cheek against gums and teethagainst gums and teeth
 preventsprevents accumulation of foodaccumulation of food in the vestibulein the vestibule

MANDIBULAR MOVEMENTS ANDMANDIBULAR MOVEMENTS AND
ROLE PLAYED BY MUSCLESROLE PLAYED BY MUSCLES
 Elevation of mandibleElevation of mandible
 TheThe temporalistemporalis elevates the coronoid processelevates the coronoid process
 Masseter and medial pterygoidMasseter and medial pterygoid elevate the angle ofelevate the angle of
mandiblemandible
 Lateral pterygoid relaxes as muscles exert upwardLateral pterygoid relaxes as muscles exert upward
tractiontraction
 Depression of mandibleDepression of mandible
 Lateral pterygoidLateral pterygoid exerts a forward pull on neck ofexerts a forward pull on neck of
mandiblemandible
 Sup. HeadSup. Head of lateral pterygoid pulls articular discof lateral pterygoid pulls articular disc
down of articular tubercledown of articular tubercle
 AccessoryAccessory muscle help in drawing mandible down.muscle help in drawing mandible down.

 Protrusion of mandibleProtrusion of mandible
 Lateral pterygoid and medial pterygoidLateral pterygoid and medial pterygoid
contractscontracts
 Retrusion of mandibleRetrusion of mandible
 Posterior fibers ofPosterior fibers of TemporalisTemporalis with help ofwith help of
Mylohyoid, Digastric & Geniohyoid draw theMylohyoid, Digastric & Geniohyoid draw the
mandible backwardsmandible backwards
 Lateral shift of mandibleLateral shift of mandible
 contraction ofcontraction of lateral pterygoidlateral pterygoid on one sideon one side
and medial pterygoid on the other side.and medial pterygoid on the other side.

ActionsActions

Articular DiscArticular Disc

DEVELOPMENT OF THEDEVELOPMENT OF THE
MUSCLES OF MASTICATIONMUSCLES OF MASTICATION
 All the muscles of mastication develop from theAll the muscles of mastication develop from the
mesoderm ofmesoderm of 11stst
brachial archbrachial arch (mandibular arch)(mandibular arch)
 Therefore, they are supplied byTherefore, they are supplied by mandibular nerve.mandibular nerve.
 Accessory muscles:-Accessory muscles:-
 DigastricDigastric -- 11stst
ARCHARCH
 MylohyoidMylohyoid -- 11stst
ARCHARCH
 GeniohyoidGeniohyoid -- Upper cervical somitesUpper cervical somites
 PlatysmaPlatysma -- 22ndnd
ARCHARCH
 BuccinatorBuccinator -- 22ndnd
ARCHARCH

DevelopmentDevelopment

Temporalis muscle

MasseterMasseter

Jaw reflexesJaw reflexes

ForceForce

APPLIED ANATOMYAPPLIED ANATOMY
The contraction of muscles of mastication affects theThe contraction of muscles of mastication affects the
displacement of fracturedisplacement of fracture
 Action of these muscles minimize displacement inAction of these muscles minimize displacement in
favorablefavorable fracturefracture
 In case ofIn case of unfavorableunfavorable fracture they tend to contribute tofracture they tend to contribute to
fracture displacementfracture displacement
 When angle fracture isWhen angle fracture is horizontalhorizontal the maseter, temporalis,the maseter, temporalis,
medial pterygoid cause upward and medial displacement ofmedial pterygoid cause upward and medial displacement of
proximal segmentproximal segment
 When angleWhen angle fracturefracture is vertical the medial and lateralis vertical the medial and lateral
pterygoid results in medial displacement of proximalpterygoid results in medial displacement of proximal
segmentsegment www.indiandentalacademy.com

FractureFracture

Undifferentiated painUndifferentiated pain

DISORDERS OF MUSCLESDISORDERS OF MUSCLES
 MYASTHENIA GRAVISMYASTHENIA GRAVIS
 TRISMUSTRISMUS
 MYOFACIAL PAIN DYSFUNCTIONMYOFACIAL PAIN DYSFUNCTION
SYNDROMESYNDROME

MYASTHENIA GRAVISMYASTHENIA GRAVIS
 It is a chronic disease withIt is a chronic disease with progressiveprogressive
weaknessweakness of skeletal muscles caused byof skeletal muscles caused by
destruction ofdestruction of acetyl cholineacetyl choline receptors atreceptors at
neuromuscular junction.neuromuscular junction.
 This isThis is autoimmune conditionautoimmune condition..
 Muscles of mastication are involved beforeMuscles of mastication are involved before
any other muscle group.any other muscle group.
 Difficulty in mastication ,deglutition andDifficulty in mastication ,deglutition and
dropping of jaw is seen.dropping of jaw is seen.

TRISMUSTRISMUS
Stiffness of muscles of masticationStiffness of muscles of mastication
 EtiologyEtiology
 Local infectionLocal infection –pericoronitis, dentoalveolar abscess–pericoronitis, dentoalveolar abscess
 DirectDirect traumatrauma to muscles of masticationto muscles of mastication
 PressurePressure is on Medial Pterygoid and Masseter leadingis on Medial Pterygoid and Masseter leading
to irritation and consequent spasmto irritation and consequent spasm
 TETANUSTETANUS
 Infection is caused byInfection is caused by clostridium tetanusclostridium tetanus whichwhich
releases powerful endotoxin thus destroying thereleases powerful endotoxin thus destroying the
spinal inhibition, thus causing uncontrolled musclespinal inhibition, thus causing uncontrolled muscle
spasmspasm
 In muscles of mastication it causesIn muscles of mastication it causes lock jawlock jaw

ParalysisParalysis
 To test theTo test the motor functionmotor function of the fifthof the fifth
nerve we ask the patient tonerve we ask the patient to clench hisclench his
teethteeth..
 TheThe TemporalTemporal and theand the MasseterMasseter musclemuscle
should stand out withshould stand out with equal prominenceequal prominence onon
each side.each side.
 If paralysis onIf paralysis on one sideone side thenthen
 Muscles wont become prominent on that sideMuscles wont become prominent on that side
 If asked to open mouth jaw willIf asked to open mouth jaw will deviatedeviate
towards the paralysed side.towards the paralysed side.

MYOFACIAL PAINMYOFACIAL PAIN
DYSFUNCTION SYNDROMEDYSFUNCTION SYNDROME
Spasm of musclesSpasm of muscles of mastication occurs due toof mastication occurs due to
 OveruseOveruse
 TraumaTrauma
 StressStress
 StrainStrain
Signs and symptomsSigns and symptoms
 Unilateral dullUnilateral dull painpain in earin ear
 TendernessTenderness of one or more muscles ofof one or more muscles of
mastication on palpationmastication on palpation
 LimitationLimitation or deviation of mandibular openingor deviation of mandibular opening
 ClickingClicking or popping at TMJor popping at TMJ

Muscles and MalocclusionMuscles and Malocclusion
 According toAccording to Moss theoryMoss theory, as growth of, as growth of
jaws depends on the activity of muscles,jaws depends on the activity of muscles,
excessive muscle activity canexcessive muscle activity can restrictrestrict
growth.growth.
 Even no use of muscle can lead to itsEven no use of muscle can lead to its
dystrophydystrophy and no development of jaws.and no development of jaws.

FunctionsFunctions
 SpeechSpeech
 Swallowing and deglutitionSwallowing and deglutition
 MasticationMastication
 Postural rest position of mandiblePostural rest position of mandible

CONCLUSIONCONCLUSION
Muscles of mastication help in chewing,Muscles of mastication help in chewing,
elevating protruding, retruding andelevating protruding, retruding and
lateral shifting oflateral shifting of mandibular movementsmandibular movements..
It also helps in speech, thus it is importantIt also helps in speech, thus it is important
for afor a normal physical healthnormal physical health which leads towhich leads to
a secure psychological influencea secure psychological influence

BibliographyBibliography
 B.D.Chaurasia’s Human Anatomy Vol 3 3rd
Edt. Pg. 181-
191
 G.J.Romanes-cunnigham’s Manual Of Practical Anatomy
15th
Ed. Vol 3 Pg 139-143.
 Peter L Williams Et Al- Gray’s Anatomy 38th
Edt. Pg 1726-
1732
 Richard S Snell-clinical Anatomy For Medical Student 5th
Ed. Pg 737-740
 Ming J Lee- Grants Atlas Of Anatomy 10th
Edition Pg 678-
680
 Mc Minn Hutchings- Color Atlas Of Anatomy 3rd
Ed. Pg 50-
51
 John W Rohan, Chihiro, Elke Lutjer- Color Atlas Of
Anatomy 9th
Edition
 Loe,mcgrager’s Synopsis Of Surgical Anatomy 12th
Ed.Pg
373

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