Cranio facial musculature

Craniofacial musculature
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Contents:-Contents:-
 introductionintroduction
Development of the muscles.Development of the muscles.
 classification of craniofacial musculature.classification of craniofacial musculature.
 the buccinator mechanism.the buccinator mechanism.
 the orbicularis oris.the orbicularis oris.
 the muscles of mastication.the muscles of mastication.
 accessory muscles of masticationaccessory muscles of mastication
 The tongue.The tongue.

The temporo mandibular jointThe temporo mandibular joint
Physiology of muscles.Physiology of muscles.
Reflex of musclesReflex of muscles
 myotactic reflex.myotactic reflex.
Methods to study muscles.Methods to study muscles.
EmgEmg
Is it the one of them?Is it the one of them?
The equilibrium theoryThe equilibrium theorywww.indiandentalacademy.comwww.indiandentalacademy.com

 Muscle and growth.Muscle and growth.
 Muscle adaptation in malocclusionMuscle adaptation in malocclusion
 Soft tissue environment of patients withSoft tissue environment of patients with
malocclusion.malocclusion.
 Muscular adaptation after orthognathic surgeryMuscular adaptation after orthognathic surgery
 Effects of orthodontic treatment on theEffects of orthodontic treatment on the
neuromuscular functions.neuromuscular functions.
 Muscles and its treatment modalities.Muscles and its treatment modalities.
 ConclusionConclusion

Introduction:-Introduction:-
 A Man to increase the strength ofA Man to increase the strength of
skeleton has been blessed by 639skeleton has been blessed by 639
muscles which includes 6 million ofmuscles which includes 6 million of
muscle fibers.muscle fibers.
 Each fibers has 1000 fibrilsEach fibers has 1000 fibrils
 Thus there is 6000 billion muscle fiberThus there is 6000 billion muscle fiber
working at one time.working at one time.

 In orthodontics and in real life weIn orthodontics and in real life we
judge / diagnose a individual when wejudge / diagnose a individual when we
look at him.look at him.
 But here when we look at patient weBut here when we look at patient we
look at him in repose/rest and we try tolook at him in repose/rest and we try to
see the dentofacial complex and theirsee the dentofacial complex and their
intimate relationship to each otherintimate relationship to each other

 This is just the static analysis but importantThis is just the static analysis but important
is the dynamic appreciation on how theyis the dynamic appreciation on how they
function , as they function, how they affectfunction , as they function, how they affect
the growth and the relationships of parts ,the growth and the relationships of parts ,
these constitutes the stomatoganthicthese constitutes the stomatoganthic
system.system.
 Here musculature plays a very importantHere musculature plays a very important
part.part.

 We orthodontist try to achieve theWe orthodontist try to achieve the
perfect equilibrium between the part ofperfect equilibrium between the part of
stomatoganthic system which includesstomatoganthic system which includes
the muscle.the muscle.
 so it is of definite importance that weso it is of definite importance that we
should know in and out about them.should know in and out about them.

Development of muscle.Development of muscle.
During the 3rd week of I.U life the embryo undergoes gastrulation toDuring the 3rd week of I.U life the embryo undergoes gastrulation to
form a trilaminar disk i.e.form a trilaminar disk i.e.
the cells from epiblast migrate to primitive streak and to primitivethe cells from epiblast migrate to primitive streak and to primitive
node detach from the epiblast and they invaginated the hypoblast tonode detach from the epiblast and they invaginated the hypoblast to
displace it and form the three layers.displace it and form the three layers.
 Three germ layers derived from the epiblastThree germ layers derived from the epiblast
 endodermendoderm
 mesodermmesoderm
 ectodermectoderm
Three germ layers derived
from the cells epiblast

The mesodermal layer is further dividedThe mesodermal layer is further divided
into:-into:-
 headhead
 paraxialparaxial
 intermediateintermediate
 laterallateral
 The mesoderm on either side of the notochordalThe mesoderm on either side of the notochordal
process thickens to form longitudinal columns ofprocess thickens to form longitudinal columns of
tissue called the paraxial mesoderm.tissue called the paraxial mesoderm.
 These segments into paired blocks of tissueThese segments into paired blocks of tissue
called the somites. Of these the cranial ones arecalled the somites. Of these the cranial ones are
called as somitomeres.called as somitomeres.

There are seven of somitomeres approx. InThere are seven of somitomeres approx. In
register with that of the pharyngeal arches.register with that of the pharyngeal arches.
The skeletal muscles of the head and neckThe skeletal muscles of the head and neck
develop from this somitomeres and the mostdevelop from this somitomeres and the most
cranial somites.cranial somites.
The pharyngeal arches develop during theThe pharyngeal arches develop during the
4th wk. of the I.U life.4th wk. of the I.U life.
They significantly contribute to theThey significantly contribute to the
development of head, face neck and nasaldevelopment of head, face neck and nasal
cavity, mouth and to some extent the larynxcavity, mouth and to some extent the larynx
and the pharynx.and the pharynx.

 The branchial arches have incomplete cleftsThe branchial arches have incomplete clefts
between the arches, the external ectodermalbetween the arches, the external ectodermal
branchial grooves and internal endodermalbranchial grooves and internal endodermal
pharyngeal pouches.pharyngeal pouches.
 The branchial groove of the first branchial archThe branchial groove of the first branchial arch
persists as external acoustic meatus which ispersists as external acoustic meatus which is
covered by the tympanic membrane.covered by the tympanic membrane.
 All the grooves disappear but they remain asAll the grooves disappear but they remain as
the tympanic cavity, auditory tube, tonsil,the tympanic cavity, auditory tube, tonsil,
thymus, parathyroid, and the thyroid gland.thymus, parathyroid, and the thyroid gland.

Cartilage components derived fromCartilage components derived from
pharyngeal arches are:-pharyngeal arches are:-
 Arch I [mandibular arch]:-Arch I [mandibular arch]:- this is major contributor tothis is major contributor to
the development of the face.the development of the face.
 The cartilage of the first arch is called as theThe cartilage of the first arch is called as the meckelsmeckels
cartilagecartilage..
 The dorsal end of the meckels cartilage becomes ossifiedThe dorsal end of the meckels cartilage becomes ossified
to form 2 bones of the middle ear ossicle :-to form 2 bones of the middle ear ossicle :-
1.1. malleusmalleus
2.2. IncusIncus
 The middle portion of the meckels cartilage regresses, butThe middle portion of the meckels cartilage regresses, but
its perichondrium forms the sphenomandibular ligament.its perichondrium forms the sphenomandibular ligament.

 The ventral part of the meckels cartilageThe ventral part of the meckels cartilage
forms a horse shaped structure in the shapeforms a horse shaped structure in the shape
of the future mandible.of the future mandible.
 The mesenchymal tissue lateral to theThe mesenchymal tissue lateral to the
cartilage undergoes intra membranouscartilage undergoes intra membranous
ossification to produce the mandible as theossification to produce the mandible as the
original meckels cartilage disappears.original meckels cartilage disappears.

 Arch II [hyoid arch]:-Arch II [hyoid arch]:- this cartilage isthis cartilage is
called as thecalled as the reicherts cartilagereicherts cartilage
 It dorsal end becomes ossified to produceIt dorsal end becomes ossified to produce
the other middle ear ossicle, the stapes, andthe other middle ear ossicle, the stapes, and
the styloid process of the temporal bone.the styloid process of the temporal bone.
 A portion of the perichondrium of theA portion of the perichondrium of the
cartilage forms the stylohyoid ligament.cartilage forms the stylohyoid ligament.
 This also contributes in the development ofThis also contributes in the development of
the hyoid bone specially the lesser cornu,the hyoid bone specially the lesser cornu,
and the superior portion of the body.and the superior portion of the body.

 The cartilage of the 3rd arch gives rise toThe cartilage of the 3rd arch gives rise to
the greater cornu and the inferior part of thethe greater cornu and the inferior part of the
body of the hyoid bone.body of the hyoid bone.
 The cartilage of the 4th and the 6th archesThe cartilage of the 4th and the 6th arches
fuses together to form the laryngealfuses together to form the laryngeal
cartilage, including the thyroid, cricoids, andcartilage, including the thyroid, cricoids, and
arytenoids cartilage except the epiglottis.arytenoids cartilage except the epiglottis.

Muscle components :-Muscle components :-
 They are derived from the cranialThey are derived from the cranial
somites and the cells that migrate atsomites and the cells that migrate at
this region from the somitomeres.this region from the somitomeres.
 Arch I:Arch I: muscles derived are: themuscles derived are: the
muscles of mastication, anterior bellymuscles of mastication, anterior belly
of digastric, mylohyoid, tensor veliof digastric, mylohyoid, tensor veli
palatine, tensor tympani.palatine, tensor tympani.

 Arch II: the muscles of facial expression.Arch II: the muscles of facial expression.
These are relatively thinner and haveThese are relatively thinner and have
their origin and insertion in the skin andtheir origin and insertion in the skin and
are present throughout the face and theare present throughout the face and the
neck.neck.
 Arch III: it gives rise to stylopharyngeousArch III: it gives rise to stylopharyngeous
muscle.muscle.
 Arch IV and arch V: - muscles of theArch IV and arch V: - muscles of the
pharynx and the larynx. Arch IV give risepharynx and the larynx. Arch IV give rise
to cricothyroid and arch V to intrinsicto cricothyroid and arch V to intrinsic
muscles of larynx.muscles of larynx.www.indiandentalacademy.comwww.indiandentalacademy.com

Classification ofClassification of
muscles:-muscles:-
they can be primarily classified as:-they can be primarily classified as:-
1.1. facial musclesfacial muscles
2.2. Muscles of mastication.Muscles of mastication.
 The facial muscles: they are related to theThe facial muscles: they are related to the
orbital margins plus the eyelids, theorbital margins plus the eyelids, the
external nose & nostrils, the lips, cheeks,external nose & nostrils, the lips, cheeks,
mouth, the pinna, scalp and the cervicalmouth, the pinna, scalp and the cervical
skin.skin.
 These are also called as muscles of facialThese are also called as muscles of facial
expression as that is their function.expression as that is their function.

 Muscles of mastication: they are chieflyMuscles of mastication: they are chiefly
concerned with the movements of theconcerned with the movements of the
TMJTMJ
 The division reflects the differentThe division reflects the different
embryonic origins and innervations of theembryonic origins and innervations of the
two groups.two groups.
 But all the functions such as mastication,But all the functions such as mastication,
deglutition, respiration, swallowing,deglutition, respiration, swallowing,
speech, communicative and emotionalspeech, communicative and emotional
expression, ocular, nasal and aural actionexpression, ocular, nasal and aural action
are the effect of close cooperation of twoare the effect of close cooperation of two
groups.groups.

According to moyers:-According to moyers:-
1.1. facial musclesfacial muscles
2.2. jaw musclesjaw muscles
3.3. Portal muscles.Portal muscles.

Characteristics of the facialCharacteristics of the facial
muscles:-muscles:-
 The primary function is expression of the emotions.The primary function is expression of the emotions.
 The facial muscles are capable of performing 7000The facial muscles are capable of performing 7000
expressions according to Coleman.expressions according to Coleman.
 They are also responsible for the maintenance ofThey are also responsible for the maintenance of
the posture of the facial structures.the posture of the facial structures.
 Paresis of the orbicularis oculi leads to theParesis of the orbicularis oculi leads to the
drooping of the lower eyelid.drooping of the lower eyelid.
 Paralysis of the orbicularis oris will lead to angularParalysis of the orbicularis oris will lead to angular
cheliosis and the drooling.cheliosis and the drooling.

The facial muscle also contributes toThe facial muscle also contributes to
stabilization of the mandible duringstabilization of the mandible during
the infantile swallowing and chewingthe infantile swallowing and chewing
and swallowing in the occlusallyand swallowing in the occlusally
compromised adults.compromised adults.
It is also important for the visual andIt is also important for the visual and
the spoken communications.the spoken communications.

Characteristics of the jawCharacteristics of the jaw
muscles:-muscles:-
 The mandible being maintained against theThe mandible being maintained against the
gravity by the stretch reflex of the elevators.gravity by the stretch reflex of the elevators.
 EMG studies have shown of [postural position]EMG studies have shown of [postural position]
that the inframandibular groups of muscles arethat the inframandibular groups of muscles are
more active than the levator.more active than the levator.
 Mandibular movement assisted by the levatorMandibular movement assisted by the levator
and the depressors can’t be considered just theand the depressors can’t be considered just the
interplay between these 2 but is very muchinterplay between these 2 but is very much
thought as the intricate muscular web where thethought as the intricate muscular web where the
teeth and the joints acts as the stops.teeth and the joints acts as the stops.

 The head posture also affects the posture of theThe head posture also affects the posture of the
mandible for e.g. when there is extension of themandible for e.g. when there is extension of the
head there is increase in the freeway space andhead there is increase in the freeway space and
when there is flexion there is decrease in thewhen there is flexion there is decrease in the
freeway space.freeway space.
 Changes in the head posture also results changesChanges in the head posture also results changes
in the anteroposterior positioning of the posture ofin the anteroposterior positioning of the posture of
the mandible.the mandible.
 One of the most important factors is the posture ofOne of the most important factors is the posture of
the mandible affecting the development of thethe mandible affecting the development of the
jaws.jaws.
 E.g. during the mouth breathing there is effect onE.g. during the mouth breathing there is effect on
the growth of both maxilla as well as the mandiblethe growth of both maxilla as well as the mandible
due to alteration in position of the mandible, hyoiddue to alteration in position of the mandible, hyoid
and the tongue.and the tongue.

 But in case where there is Sunday biteBut in case where there is Sunday bite
there is no resultant correction probablythere is no resultant correction probably
because the dorsal position of thebecause the dorsal position of the
mandible during the functional activitiesmandible during the functional activities
cancels the biologic signals to the jointcancels the biologic signals to the joint
structures.structures.
 Thus functional appliances work the bestThus functional appliances work the best
as they are worn for the most hours of theas they are worn for the most hours of the
day .day .

Characteristics of the portalCharacteristics of the portal
muscles:-muscles:-
 Portal muscle is the word coined byPortal muscle is the word coined by
Bosma to denote the upper alimentaryBosma to denote the upper alimentary
tract and the respiratory tract.tract and the respiratory tract.
 These muscles serve some functions ofThese muscles serve some functions of
our interest such as posture, respiration,our interest such as posture, respiration,
feeding.feeding.

 The muscles include the muscles ofThe muscles include the muscles of
the tongue [both the intrinsic and thethe tongue [both the intrinsic and the
extrinsic] the soft palate, theextrinsic] the soft palate, the
pharyngeal pillars, the pharynx proper,pharyngeal pillars, the pharynx proper,
and the larynx.and the larynx.

According to grays:-According to grays:-
 they are broadly classifies as:they are broadly classifies as:
1.1. epicranial musclesepicranial muscles
2.2. circumorbital musclescircumorbital muscles
3.3. the nasal musculaturethe nasal musculature
4.4. the buccolabial musculaturethe buccolabial musculature

The epicranial musculatureThe epicranial musculature
The epicranius consists of two mainThe epicranius consists of two main
partsparts
1.1. occipitofrontalisoccipitofrontalis
2.2. Temporoparietalis.Temporoparietalis.

The scalp:-The scalp:-
 The scalp essentially consists of fiveThe scalp essentially consists of five
layers i.e.layers i.e.
1.1. superficial fasciasuperficial fascia
2.2. connective tissueconnective tissue
3.3. epicranial aponeurosisepicranial aponeurosis
4.4. loose aerolar tissueloose aerolar tissue
5.5. pericraniumpericranium

 The superficial fascia in the scalp is firm andThe superficial fascia in the scalp is firm and
fibro-adipose adherent to the skin and thefibro-adipose adherent to the skin and the
underlying epicranius and the aponeurosis,underlying epicranius and the aponeurosis,
the galea aponeurotica [epicranialthe galea aponeurotica [epicranial
aponeurosis.]aponeurosis.]
 It is continuous with the superficial fascia ofIt is continuous with the superficial fascia of
the back of the neck; laterally, it is prolongedthe back of the neck; laterally, it is prolonged
to the temporal region where it losses itsto the temporal region where it losses its
texture.texture. www.indiandentalacademy.comwww.indiandentalacademy.com

The occipito frontalisThe occipito frontalis
 It is a broad, musculofibrous layer,It is a broad, musculofibrous layer,
covers the dome of the skull, from thecovers the dome of the skull, from the
nuchal lines to the eyebrows.nuchal lines to the eyebrows.
 It consists of 4 parts---- 2 occipital andIt consists of 4 parts---- 2 occipital and
2 frontal connected by the epicranial2 frontal connected by the epicranial
aponeurosisaponeurosis

 Occipital part: - each of them are thin,Occipital part: - each of them are thin,
quadrilateral arises by tendinous fibersquadrilateral arises by tendinous fibers
from the lat. 2/3rd of the highest nuchalfrom the lat. 2/3rd of the highest nuchal
lines of the occipital bone and the mastoidlines of the occipital bone and the mastoid
part of the temporal bone. It ends in thepart of the temporal bone. It ends in the
epicranial aponeurosis.epicranial aponeurosis.
 Frontal part: - they are thin, quadrilateral,Frontal part: - they are thin, quadrilateral,
and adherent to superficial fascia. It isand adherent to superficial fascia. It is
broader than the occipital part and itsbroader than the occipital part and its
fibers are longer and paler.fibers are longer and paler.

 It has got no bony attachments. Its medial fibers areIt has got no bony attachments. Its medial fibers are
contiguous with those of the procerus; its intermediatecontiguous with those of the procerus; its intermediate
fibers blend with the corrugator supercilli and thefibers blend with the corrugator supercilli and the
orbicularis oculi; its lateral fibers are also blended withorbicularis oculi; its lateral fibers are also blended with
the latter muscle over the zygomatic process of thethe latter muscle over the zygomatic process of the
frontal bone.frontal bone.
 From these attachments the fibers are directed upwardsFrom these attachments the fibers are directed upwards
to join the epicranial aponeurosis in front of the coronalto join the epicranial aponeurosis in front of the coronal
suture. The medial margins of the frontal slips are joinedsuture. The medial margins of the frontal slips are joined
together for some distance above the root of the nose;together for some distance above the root of the nose;
but between the occipital bellies there is considerable,but between the occipital bellies there is considerable,
but variable interval occupied by the epicranialbut variable interval occupied by the epicranial
aponeurosis.aponeurosis.

Galea aponeurotica:-Galea aponeurotica:-
 It covers the upper part of the cranium andIt covers the upper part of the cranium and
along with the epicranius it forms thealong with the epicranius it forms the
continuous fibromuscular sheet extendingcontinuous fibromuscular sheet extending
from the occipital to the eyebrows. Behind, infrom the occipital to the eyebrows. Behind, in
the interval between the occipital parts of thethe interval between the occipital parts of the
occipitofrontalis, it is attached on theoccipitofrontalis, it is attached on the
external protuberance or highest nuchalexternal protuberance or highest nuchal
lines of the occipital bone.lines of the occipital bone.
 In front it splits to enclose the frontal partsIn front it splits to enclose the frontal parts
and sends a short narrow prolongationand sends a short narrow prolongation
between them.between them. www.indiandentalacademy.comwww.indiandentalacademy.com

 It is united to the skin by firm, fibrousIt is united to the skin by firm, fibrous
superficial fascia; it is connected to thesuperficial fascia; it is connected to the
pericranium by loose aerolar tissuepericranium by loose aerolar tissue
which allows its free movement. Thewhich allows its free movement. The
latter carrying it with the skin of the scalplatter carrying it with the skin of the scalp
 Nerve supply: - the occipital part isNerve supply: - the occipital part is
supplied by the posterior auricularsupplied by the posterior auricular
branch and the frontal part by thebranch and the frontal part by the
temporal branches of the facial nerve.temporal branches of the facial nerve.

 Action:- the occipital slips draw theAction:- the occipital slips draw the
scalp downward , the frontal slipsscalp downward , the frontal slips
acting from above raise the eyebrowsacting from above raise the eyebrows
and the skin of the root of the nose ;and the skin of the root of the nose ;
acting from below they draw the scalpacting from below they draw the scalp
forwards; throwing the integument offorwards; throwing the integument of
the forehead into transverse wrinkles.the forehead into transverse wrinkles.
 They act in tandem in expressionThey act in tandem in expression
like surprise, horror or fright etc.like surprise, horror or fright etc.

 The fourth layer of the scalp:The fourth layer of the scalp:
 it is made up of loose aerolar tissue. itit is made up of loose aerolar tissue. it
extends anteriorly to the eyelids; andextends anteriorly to the eyelids; and
posteriorly to the highest nuchal linesposteriorly to the highest nuchal lines
and on each side to the superiorand on each side to the superior
temporal lines.temporal lines.
 The fifth layer is called as pericranium:-itThe fifth layer is called as pericranium:-it
is loosely attached to the surface of theis loosely attached to the surface of the
bones, but is firmly adherent to theirbones, but is firmly adherent to their
sutures where the sutural ligaments bindsutures where the sutural ligaments bind
the pericranium to the endocranium.the pericranium to the endocranium.

Temporoparietalis:-Temporoparietalis:-
 It is variably developed sheet of muscle thatIt is variably developed sheet of muscle that
lies between the frontal part of the occipitolies between the frontal part of the occipito
frontalis and the ant. And sup. Auricularfrontalis and the ant. And sup. Auricular
muscles.muscles.
 A thin muscular slip, the transverse nuchae,A thin muscular slip, the transverse nuchae,
is present in about 25 percent of the people;is present in about 25 percent of the people;
it arises from the external occipitalit arises from the external occipital
protuberance or from the superior nuchalprotuberance or from the superior nuchal
lines, present either sup. Or deep tolines, present either sup. Or deep to
trapezius; it is frequently inserted with thetrapezius; it is frequently inserted with the
auricularis posterior, but may join the post.auricularis posterior, but may join the post.
Edge of the sterocleidomastoid.Edge of the sterocleidomastoid.

Circumorbital andCircumorbital and
palpeberal musculature.palpeberal musculature.
The muscle that come under thisThe muscle that come under this
heading are:-heading are:-
1.1. orbicularis oculiorbicularis oculi
2.2. corrugator supercillicorrugator supercilli
3.3. levator palpebrae superiorislevator palpebrae superioris

The orbicularis oculi:-The orbicularis oculi:-
 it is a broad, flat, elliptical muscle thatit is a broad, flat, elliptical muscle that
occupies the eyelids, surrounds theoccupies the eyelids, surrounds the
circumference of the orbit and spreadscircumference of the orbit and spreads
on the temporal region and the cheek.on the temporal region and the cheek.
it consists of the orbital , palpebraeit consists of the orbital , palpebrae
and lacrimal parts.and lacrimal parts.

The orbital partThe orbital part
 it is reddish and thicker than the palpeberalit is reddish and thicker than the palpeberal
fasiculifasiculi
 Origin:-arises from the nasal part of the frontalOrigin:-arises from the nasal part of the frontal
bone, from the frontal process of the maxilla andbone, from the frontal process of the maxilla and
from the medial palpeberal ligament, whichfrom the medial palpeberal ligament, which
interrupts the bony attachment.interrupts the bony attachment.
 It fibers form the complete ellipses without theIt fibers form the complete ellipses without the
interruption on the lateral side, the upper onesinterruption on the lateral side, the upper ones
blending with the frontal part of theblending with the frontal part of the
occipitofrontalis and the corrugator.occipitofrontalis and the corrugator.www.indiandentalacademy.comwww.indiandentalacademy.com

 Insertion:-some of the fibers areInsertion:-some of the fibers are
inserted into the skin and theinserted into the skin and the
subcutaneous tissue of the eyebrow.subcutaneous tissue of the eyebrow.
They constitute the depressorThey constitute the depressor
supercilli.supercilli.

The palpeberal partThe palpeberal part
 - it is thin and pale. It arises from the medial- it is thin and pale. It arises from the medial
palpeberal ligament chiefly from its superficialpalpeberal ligament chiefly from its superficial
but also from its deep parts, though not frombut also from its deep parts, though not from
the lower margin, it arises also from the bonethe lower margin, it arises also from the bone
immd. Above and below the ligament.immd. Above and below the ligament.
 The fibers sweep across the eyelids in front ofThe fibers sweep across the eyelids in front of
the orbital septum and at the lateralthe orbital septum and at the lateral
commissure and interlace to form the lateralcommissure and interlace to form the lateral
palpeberal raphe. A small group of the finepalpeberal raphe. A small group of the fine
fibers lies close to the margin of each eyelid,fibers lies close to the margin of each eyelid,
behind the eyelashes; it is named as the ciliarybehind the eyelashes; it is named as the ciliary
bundle.bundle. www.indiandentalacademy.comwww.indiandentalacademy.com

The lacrimal part: -The lacrimal part: -
 it lies behind the lacrimal sac but separatedit lies behind the lacrimal sac but separated
from it by the lacrimal fascia.from it by the lacrimal fascia.
 It is attached to lacrimal fascia, to the upperIt is attached to lacrimal fascia, to the upper
part of the crest of the lacrimal bone, andpart of the crest of the lacrimal bone, and
adjacent part of the lateral part of the lacrimaladjacent part of the lateral part of the lacrimal
bone.bone.
 Passing laterally behind the lacrimal sac thePassing laterally behind the lacrimal sac the
muscle divides into upper and lower slips; somemuscle divides into upper and lower slips; some
fibers are inserted into the tarsi of the eyelidsfibers are inserted into the tarsi of the eyelids
close to the lacrimal canaliculi, but mostclose to the lacrimal canaliculi, but most
continue across in front of the tarsi andcontinue across in front of the tarsi and
interlace in the lateral palpeberal raphe.interlace in the lateral palpeberal raphe.

 The medial palpeberal ligament:- it isThe medial palpeberal ligament:- it is
about 4mm in the length and 2mm in theabout 4mm in the length and 2mm in the
breadth, is attached to the frontalbreadth, is attached to the frontal
process of the maxilla in front of theprocess of the maxilla in front of the
nasolacrimal groove. Crossing thenasolacrimal groove. Crossing the
lacrimal sac it divides into 2 parts i.e.lacrimal sac it divides into 2 parts i.e.
upper and lower parts each one attachedupper and lower parts each one attached
to the medial end of the correspondingto the medial end of the corresponding
tarsus.tarsus.
 It is separated from the lacrimal sacIt is separated from the lacrimal sac
by the fascia.by the fascia.

 Nerve supply: - temporal and zygomaticNerve supply: - temporal and zygomatic
branch of the facial nerve.branch of the facial nerve.
 Actions: - the orbicularis oculi: - it is theActions: - the orbicularis oculi: - it is the
sphincter muscle of the eyelids.sphincter muscle of the eyelids.
 The palpeberal portionThe palpeberal portion acts underacts under
voluntary control closing the lids gently asvoluntary control closing the lids gently as
in sleep or blinking; the orbital portion isin sleep or blinking; the orbital portion is
more frequently under voluntary controlmore frequently under voluntary control

 During the eye closure there is lowering ofDuring the eye closure there is lowering of
the upper as well as elevation of the lowerthe upper as well as elevation of the lower
eyelid. thus palpeberal part has depressoreyelid. thus palpeberal part has depressor
and elevator fasicles.when the entireand elevator fasicles.when the entire
muscle contracts than the skin of themuscle contracts than the skin of the
forehead , temple and cheek is drawnforehead , temple and cheek is drawn
towards the medial angle of the orbit, andtowards the medial angle of the orbit, and
the eyelids are not only firmly closed butthe eyelids are not only firmly closed but
they are moved in toto medially. The skin isthey are moved in toto medially. The skin is
thrown in the folds on the lateral angle ofthrown in the folds on the lateral angle of
the eyelids due to this action which arethe eyelids due to this action which are
called as crow’s feet.called as crow’s feet.

 The lacrimal part of the muscle draws the eyelidsThe lacrimal part of the muscle draws the eyelids
and the lacrimal papillae medially, and exertsand the lacrimal papillae medially, and exerts
traction on the lacrimal fascia and it dilates thetraction on the lacrimal fascia and it dilates the
lacrimal sac.lacrimal sac.
 Thus the muscle has important action in tearThus the muscle has important action in tear
transport.transport.
 The muscle is also an important element in facialThe muscle is also an important element in facial
expression and the ocular reflexes.expression and the ocular reflexes.
 Partial closure of the palpeberal fissure togetherPartial closure of the palpeberal fissure together
with bunching and the protrusion of the eyebrowswith bunching and the protrusion of the eyebrows
diminish the entry of the light.diminish the entry of the light.

 These action of the upper orbital fibersThese action of the upper orbital fibers
and their peripheral extension causeand their peripheral extension cause
vertical furrowing above the bridge of thevertical furrowing above the bridge of the
nose. This is called as blink reflex and itsnose. This is called as blink reflex and its
protective value is obvious.protective value is obvious.

The corrugatorThe corrugator
supercilli:supercilli:
 it is a small pyramidal muscle, at theit is a small pyramidal muscle, at the
medial end of the eyebrows, deep to themedial end of the eyebrows, deep to the
frontal part of the occipitofrontalis and thefrontal part of the occipitofrontalis and the
orbicularis oculi .orbicularis oculi .
 From the medial end of the superciliaryFrom the medial end of the superciliary
arch its fibers pass slightly laterally andarch its fibers pass slightly laterally and
slightly upwards to the deep surface ofslightly upwards to the deep surface of
the skin above the middle of thethe skin above the middle of the
supraorbital margin.supraorbital margin.www.indiandentalacademy.comwww.indiandentalacademy.com

 Nerve supply: - the temporal branches ofNerve supply: - the temporal branches of
the facial nerve.the facial nerve.
 Action: - draws the eyebrows mediallyAction: - draws the eyebrows medially
and downwardsand downwards
 Together with the orbicularis oculiTogether with the orbicularis oculi
causing vertical wrinkles of the forehead.causing vertical wrinkles of the forehead.
 It assists in drawing the eyebrowsIt assists in drawing the eyebrows
downwards in the bright sunlight and isdownwards in the bright sunlight and is
also involved in frowningalso involved in frowning

The nasal musculature:The nasal musculature:
This group comprises of threeThis group comprises of three
muscles:-muscles:-
1.1. the procerusthe procerus
2.2. the nasalisthe nasalis
3.3. The depressor septi.The depressor septi.

The procerus: -The procerus: -
 it is a small pyramidal slip continuous withit is a small pyramidal slip continuous with
the medial side of the frontal part of thethe medial side of the frontal part of the
occipitofrontalis.occipitofrontalis.
 Origin:-It arises from the fascia coveringOrigin:-It arises from the fascia covering
the lower part of the nasal bone and thethe lower part of the nasal bone and the
upper part of the lateral nasal cartilage.upper part of the lateral nasal cartilage.
 Insertion:-it is inserted into the skin overInsertion:-it is inserted into the skin over
the lower part of the forehead betweenthe lower part of the forehead between
the eyebrows.the eyebrows.

 Action: - it draws down the medial angleAction: - it draws down the medial angle
of the eyebrow and incidentally producesof the eyebrow and incidentally produces
wrinkles over the bridge of the nose.wrinkles over the bridge of the nose.
 It is active in frowning and concentration.It is active in frowning and concentration.
 It also aids in reducing the glare of theIt also aids in reducing the glare of the
sunlight.sunlight.

The nasalis: -The nasalis: -
 it consists of transverse and alar partsit consists of transverse and alar parts
which may be continuous at the origin.which may be continuous at the origin.
 The transverse part:-[compressor naris] –The transverse part:-[compressor naris] –
it arises from the maxilla just lateral to theit arises from the maxilla just lateral to the
nasal notch; its fibers proceed upwardsnasal notch; its fibers proceed upwards
and medially and expand into a thinand medially and expand into a thin
aponeurosis, which is continuous on theaponeurosis, which is continuous on the
bridge of the nose with that of the musclebridge of the nose with that of the muscle
of the opposite side, and with theof the opposite side, and with the
aponeurosis of the procerus.aponeurosis of the procerus.www.indiandentalacademy.comwww.indiandentalacademy.com

 The alar part [dilator naris]—it arises from theThe alar part [dilator naris]—it arises from the
maxilla, below and medial to the transverse part. Itmaxilla, below and medial to the transverse part. It
is attached to the cartilaginous ala nasi.is attached to the cartilaginous ala nasi.
 Actions: - the transverse part: - it compresses theActions: - the transverse part: - it compresses the
nasal aperture at the junction of the vestibule withnasal aperture at the junction of the vestibule with
the nasal cavity.the nasal cavity.
 The alar part draws the ala downwards andThe alar part draws the ala downwards and
laterally and so assists in widening the ant. Nasallaterally and so assists in widening the ant. Nasal
aperture.aperture.
 These actions are visible in deep respiration,These actions are visible in deep respiration,
especially in its inspiratory phase, and they alsoespecially in its inspiratory phase, and they also
accompany certain emotional states.accompany certain emotional states.

The depressor septi: -The depressor septi: -
 often regarded as the part of theoften regarded as the part of the
dilator nasi; is attached to maxilladilator nasi; is attached to maxilla
above the central incisor roots.above the central incisor roots.
 Present immediately deep to thePresent immediately deep to the
mucous membrane of the upper lip.mucous membrane of the upper lip.

 Action: - it assists the alar part of theAction: - it assists the alar part of the
nasalis in widening the nasal aperturenasalis in widening the nasal aperture
while deep inspiration.while deep inspiration.
 Nerve supply: - All the nasal musculatureNerve supply: - All the nasal musculature
supplied by superior buccal branches ofsupplied by superior buccal branches of
the facial nerve.the facial nerve.

buccolabial musculature:-buccolabial musculature:-
 These are the muscle slips which control theThese are the muscle slips which control the
shape of buccal orifice and the posture of theshape of buccal orifice and the posture of the
lipslips
They include: the retractors and elevators ofThey include: the retractors and elevators of
the upper lip viz:-the upper lip viz:-
1.1. levator labii superioris alaeque nasilevator labii superioris alaeque nasi
2.2. levator labii superiorislevator labii superioris
3.3. the zygomaticus majorthe zygomaticus major
4.4. the zygomaticus minorthe zygomaticus minor
5.5. risoriusrisorius
6.6. levator anguli orislevator anguli oriswww.indiandentalacademy.comwww.indiandentalacademy.com

the depressor and retractors of thethe depressor and retractors of the
lower lip viz:-lower lip viz:-
1.1. depressor labii inferiorisdepressor labii inferioris
2.2. depressor anguli orisdepressor anguli oris
3.3. mentalismentalis

The levator labii superioris alaequeThe levator labii superioris alaeque
nasinasi
 Origin:-it arises from the upper part of theOrigin:-it arises from the upper part of the
frontal process of the maxilla and, passingfrontal process of the maxilla and, passing
obliquely downwards and laterally, dividesobliquely downwards and laterally, divides
into medial and lateral slips.into medial and lateral slips.
 Insertion:-The medial slips is inserted intoInsertion:-The medial slips is inserted into
greater alar cartilage and skin of the ala ofgreater alar cartilage and skin of the ala of
the nose.the nose.

 the lateral slip is prolonged into thethe lateral slip is prolonged into the
lateral part of the upper lip, and blendslateral part of the upper lip, and blends
with the levator labii superioris andwith the levator labii superioris and
orbicularis orisorbicularis oris
 Action: - the lateral slip raises and evertsAction: - the lateral slip raises and everts
the lipthe lip
 The medial slip acts as dilator of theThe medial slip acts as dilator of the
nostril.nostril.
 Nerve supply: - it is supplied by theNerve supply: - it is supplied by the
buccal branches of the facial nerve.buccal branches of the facial nerve.

The levator labii superioris: -The levator labii superioris: -
 Origin:-it starts immediately above theOrigin:-it starts immediately above the
infra-orbital margin at the lower margininfra-orbital margin at the lower margin
of the orbital opening.of the orbital opening.
 It arises from the maxilla and theIt arises from the maxilla and the
zygomatic bone.zygomatic bone.

 Insertion:-Its fibers converge into the muscularInsertion:-Its fibers converge into the muscular
substance of the upper lip between the lateral slipsubstance of the upper lip between the lateral slip
of the levator labii superioris alaeque nasi andof the levator labii superioris alaeque nasi and
levator anguli oris.levator anguli oris.
 Action: - it raises and everts the upper lip.Action: - it raises and everts the upper lip.
 Along with the zygomaticus major it forms theAlong with the zygomaticus major it forms the
nasolabial furrow, from the side of the nose to thenasolabial furrow, from the side of the nose to the
upper lip.upper lip.
 The furrow deepens while expressing sadnessThe furrow deepens while expressing sadness
and seriousness.and seriousness.
 Nerve supply: - it is supplied by the buccalNerve supply: - it is supplied by the buccal
branches of the facial nerve.branches of the facial nerve.

The zygomaticus minor: -The zygomaticus minor: -
 Origin:-arises from the lateral surface of theOrigin:-arises from the lateral surface of the
zygomatic bone immediately behind thezygomatic bone immediately behind the
zygomaticomaxillary suture.zygomaticomaxillary suture.
 Insertion:-it passes downward and mediallyInsertion:-it passes downward and medially
into the muscular substance of the upper lip.into the muscular substance of the upper lip.
 It is separated from the levator labiiIt is separated from the levator labii
superioris by a short interval.superioris by a short interval.

 Action:-it elevates the upper lip and alsoAction:-it elevates the upper lip and also
produces the nasolabial furrow.produces the nasolabial furrow.
 When the levator labii superioris alaequeWhen the levator labii superioris alaeque
nasi, the levator labii superioris and thenasi, the levator labii superioris and the
zygomaticus minor are in action togetherzygomaticus minor are in action together
they express contempt and disdain.they express contempt and disdain.

The levator anguli oris: -The levator anguli oris: -
 Origin: it arises from the canine fossa,Origin: it arises from the canine fossa,
just below the infra –orbital margin.just below the infra –orbital margin.
 Insertion:-it is inserted into the angle ofInsertion:-it is inserted into the angle of
the mouth, intermingling with fibers of thethe mouth, intermingling with fibers of the
zygomaticus major, depressor anguli oriszygomaticus major, depressor anguli oris
and orbicularis oris...and orbicularis oris...
 Between the levator anguli oris and theBetween the levator anguli oris and the
levator labii superioris are the infra orbitallevator labii superioris are the infra orbital
vessels and nerves.vessels and nerves.

 Action: - it raises the angle of theAction: - it raises the angle of the
mouthmouth
 It is instrumental in producing theIt is instrumental in producing the
nasolabial furrow.nasolabial furrow.

The zygomaticus major: -The zygomaticus major: -
 Origin:-extends from the zygomatic boneOrigin:-extends from the zygomatic bone
in front of the zygomaticotemporal suture.in front of the zygomaticotemporal suture.
 Insertion:-to the angle of the mouth,Insertion:-to the angle of the mouth,
where it blends with the fibers of thewhere it blends with the fibers of the
levator anguli oris, orbicularis oris and thelevator anguli oris, orbicularis oris and the
depressor anguli oris.depressor anguli oris.

 Actions: - it draws the angle of the mouthActions: - it draws the angle of the mouth
upward & laterally as in laughing.upward & laterally as in laughing.
 The zygomaticus major and minor and theThe zygomaticus major and minor and the
levator labii superioris are sometimeslevator labii superioris are sometimes
enclosed by thin sheet of muscle calledenclosed by thin sheet of muscle called
as musculus malaris and are continuousas musculus malaris and are continuous
with the orbicularis oculi. [Lightoller 1925]with the orbicularis oculi. [Lightoller 1925]

The depressor labii inferioris:The depressor labii inferioris:
--
 Origin:-it is quadrilateral in shape andOrigin:-it is quadrilateral in shape and
arises from the oblique line of thearises from the oblique line of the
mandible between the mental foramenmandible between the mental foramen
and the symphysis menti. At its origin it isand the symphysis menti. At its origin it is
continuous with the platysma.continuous with the platysma.
 Insertion:-it passes upwards and mediallyInsertion:-it passes upwards and medially
into the skin of the lower lip, blending withinto the skin of the lower lip, blending with
its fellow and orbicularis oris.its fellow and orbicularis oris.

 Action - it draws the lower lip downwardAction - it draws the lower lip downward
and a little laterally in masticatoryand a little laterally in masticatory
activityactivity
 It contributes to expression of irony.It contributes to expression of irony.
 Nerve supply: - it receives supply fromNerve supply: - it receives supply from
the mandibular marginal branch of thethe mandibular marginal branch of the
facial nerve.facial nerve.

The depressor anguli oris: -The depressor anguli oris: -
 Origin:-arise from the oblique line of theOrigin:-arise from the oblique line of the
mandible, below and lateral to themandible, below and lateral to the
depressor labii inferioris.depressor labii inferioris.
 Insertion:-it converges into the narrowInsertion:-it converges into the narrow
fasciculus blending with the other musclesfasciculus blending with the other muscles
at the angle of the mouth.at the angle of the mouth.
 It is continuous with the platysma at itsIt is continuous with the platysma at its
origin and at its insertion with theorigin and at its insertion with the
orbicularis oris and risorius;orbicularis oris and risorius;

 Some of the fibers are directly continuousSome of the fibers are directly continuous
with that of the levator anguli oris, andwith that of the levator anguli oris, and
others accidentally cross to the other sideothers accidentally cross to the other side
these are called as the transversus menti.these are called as the transversus menti.
 Action: - draws the angle of the mouthAction: - draws the angle of the mouth
downward and laterally while opening ofdownward and laterally while opening of
the mouth and during expression of thethe mouth and during expression of the
sadness.sadness.

The mentalis:The mentalis:
 Origin:-it is a conical fasciculus at theOrigin:-it is a conical fasciculus at the
side of the frenulum of the lower lip. Itside of the frenulum of the lower lip. It
arises from the incisive fossa of thearises from the incisive fossa of the
mandible.mandible.
 Insertion:-it descends to be attachedInsertion:-it descends to be attached
to the skin of the chin.to the skin of the chin.

 Action:- it raises and protrude the lower lipAction:- it raises and protrude the lower lip
and at same time wrinkles the skin of theand at same time wrinkles the skin of the
chin.chin.
 It helps in drinking and in expressingIt helps in drinking and in expressing
disdain and doubt.disdain and doubt.
 There is continuous activity in the muscleThere is continuous activity in the muscle
also during the sleep according to EMGalso during the sleep according to EMG
studies.studies.

The buccinator:The buccinator:
 it is thin quadrilateral muscle occupyingit is thin quadrilateral muscle occupying
the interval between the maxilla and thethe interval between the maxilla and the
mandible, in the cheek.mandible, in the cheek.
 It is attached to the outer surfaces of theIt is attached to the outer surfaces of the
alveolar processes of the maxilla and thealveolar processes of the maxilla and the
mandible, opposite to molar region andmandible, opposite to molar region and
behind, the anterior border of thebehind, the anterior border of the
pterygomandibular raphe, whichpterygomandibular raphe, which
separates it from the superior constrictorseparates it from the superior constrictor
of the pharynx.of the pharynx. www.indiandentalacademy.comwww.indiandentalacademy.com

 Between the maxillary tuberosity and theBetween the maxillary tuberosity and the
upper end of the raphe a few fibers ariseupper end of the raphe a few fibers arise
from the tendinous band which bridge thefrom the tendinous band which bridge the
gap between the maxilla and the pterygoidgap between the maxilla and the pterygoid
hamulus.hamulus.
 The tendon of the tensor veli palatini on itsThe tendon of the tensor veli palatini on its
way to the soft plate pierces the pharyngealway to the soft plate pierces the pharyngeal
wall in the small gap which lies behind thiswall in the small gap which lies behind this
tendinous band.tendinous band.

 The fibers of the buccinator convergeThe fibers of the buccinator converge
towards the angle of the mouth , wheretowards the angle of the mouth , where
the central fibers intersect each other,the central fibers intersect each other,
those from below being continuous withthose from below being continuous with
the upper segment of the orbicularis oris,the upper segment of the orbicularis oris,
and those from above with the lowerand those from above with the lower
segment of orbicularis oris.segment of orbicularis oris.
 The lowest and the highest fibers areThe lowest and the highest fibers are
continuous forward into the correspondingcontinuous forward into the corresponding
lip without decussation.lip without decussation.

Relations:-Relations:-
 it is covered by the buccopharyngealit is covered by the buccopharyngeal
fascia and lies in the same plane asfascia and lies in the same plane as
that of the superior constrictor.that of the superior constrictor.
 Superiorly, posteriorly a large mass ofSuperiorly, posteriorly a large mass of
fat separates it from the ramus of thefat separates it from the ramus of the
mandible, masseter, and small portionmandible, masseter, and small portion
of the temporalis.this is called as theof the temporalis.this is called as the
suctorial pad.suctorial pad.

 Anteriorly, superficial surface of the muscleAnteriorly, superficial surface of the muscle
is related to the zygomaticus majoris related to the zygomaticus major
risorius, levator and depressor anguli oris,risorius, levator and depressor anguli oris,
the parotid duct which pierces it oppositethe parotid duct which pierces it opposite
to the 3rd molar tooth. the facial artery andto the 3rd molar tooth. the facial artery and
facial vein crosses it; the facial nerve andfacial vein crosses it; the facial nerve and
the buccal nerves also cross it .the buccal nerves also cross it .
 The deep surface is related to the buccalThe deep surface is related to the buccal
glands and the mucous membrane of theglands and the mucous membrane of the
mouth.mouth.

 Nerve supply: - supplied by the lowerNerve supply: - supplied by the lower
buccal branch of the facial nervebuccal branch of the facial nerve
 Action: - it compresses the cheek againstAction: - it compresses the cheek against
the teeth so helps in mastication as thethe teeth so helps in mastication as the
food is passed between them.food is passed between them.
 It helps in blowing, hence the nameIt helps in blowing, hence the name
buccinator= the trumpeter.buccinator= the trumpeter.

The buccinator mechanismThe buccinator mechanism
 There is a strong interdependence ofThere is a strong interdependence of
muscles and bone and the major factormuscles and bone and the major factor
in this environmental balance is thein this environmental balance is the
musculature. They are the potent forcemusculature. They are the potent force
whether in active state or at rest.whether in active state or at rest.
 The teeth and the supporting structureThe teeth and the supporting structure
are under constant pressure from theare under constant pressure from the
contiguous musculaturecontiguous musculature

 The integrity of the dental arch and itsThe integrity of the dental arch and its
relation with the same arch and therelation with the same arch and the
opposing arch is maintained by theopposing arch is maintained by the
morphogenetic pattern, which is modified bymorphogenetic pattern, which is modified by
the stabilizing and active functional force ofthe stabilizing and active functional force of
musclesmuscles
 Environmental factors are the contactEnvironmental factors are the contact
relations and resistance afforded by therelations and resistance afforded by the
buttressing effect of contiguous teeth,buttressing effect of contiguous teeth,
occlusal interdigitation and the bone buildingocclusal interdigitation and the bone building
– resorption balance maintained in the– resorption balance maintained in the
periodontal membrane.periodontal membrane.www.indiandentalacademy.comwww.indiandentalacademy.com

 Thus stability is dependent on the 1.Thus stability is dependent on the 1.
Genetic. 2. Environmental 3. EpigeneticGenetic. 2. Environmental 3. Epigenetic
factors 4. Morphologic factors 5.factors 4. Morphologic factors 5.
Physiologic.Physiologic.
 Acc. To Winders the tongue exerts two toAcc. To Winders the tongue exerts two to
three times more pressure on the dentitionthree times more pressure on the dentition
than the lips and the cheeks but the netthan the lips and the cheeks but the net
effect is maintained as the tonal contraction,effect is maintained as the tonal contraction,
peripheral fiber recruitment of the buccal &peripheral fiber recruitment of the buccal &
labial muscles and the atm. Pressure teamlabial muscles and the atm. Pressure team
up to offset the momentarily greaterup to offset the momentarily greater
functional force of the tongue.functional force of the tongue.

 Acc. to Lear and Moorress the enigmaAcc. to Lear and Moorress the enigma
between the dental arch and the musclebetween the dental arch and the muscle
function remains as there are limitations suchfunction remains as there are limitations such
as measuring equipment; hydraulic nature ofas measuring equipment; hydraulic nature of
response, size and sample and even theresponse, size and sample and even the
geometry of the dental arch which do notgeometry of the dental arch which do not
permit definitive form- function conclusions.permit definitive form- function conclusions.

The buccinator mechanism.The buccinator mechanism.
The orbicularis oris muscle decussating fibers joins theThe orbicularis oris muscle decussating fibers joins the
right and left fibers in the lips. The buccinator mech.right and left fibers in the lips. The buccinator mech.
Runs laterally and posteriorly around the corner of theRuns laterally and posteriorly around the corner of the
mouth, joining other fibers of the buccinator musclemouth, joining other fibers of the buccinator muscle
which insert into the pterygomandibular raphe just behindwhich insert into the pterygomandibular raphe just behind
the dentition. Here it intermingles with the fibers of thethe dentition. Here it intermingles with the fibers of the
sup. Constrictor muscle and continues posteriorly andsup. Constrictor muscle and continues posteriorly and
medially to anchor at the origin of the superior constrictormedially to anchor at the origin of the superior constrictor
muscles, the pharyngeal tubercle of the occipital bone.muscles, the pharyngeal tubercle of the occipital bone.
The tongue pressure opposes the buccinator mech.The tongue pressure opposes the buccinator mech.

The pterygomandibular raphe:The pterygomandibular raphe:
--
 It is the interlacing of the tendinous fibersIt is the interlacing of the tendinous fibers
stretched from the hamulus of the medialstretched from the hamulus of the medial
pterygoid plate to the posterior end of thepterygoid plate to the posterior end of the
mylohyoid line of the mandible.mylohyoid line of the mandible.
 Medially it is covered by the mucousMedially it is covered by the mucous
membrane of the mouth.membrane of the mouth.

 Laterally, it is separated from theLaterally, it is separated from the
ramus of the mandible by quantity oframus of the mandible by quantity of
fat.fat.
 Posteriorly, it gives attachment to thePosteriorly, it gives attachment to the
superior constrictor of the pharynx.superior constrictor of the pharynx.
 Anteriorly to the part of theAnteriorly to the part of the
buccinator.buccinator.

The orbicularis oris: -The orbicularis oris: -
 Is made of the several strata whichIs made of the several strata which
surround the orifice of the mouth butsurround the orifice of the mouth but
have different directions. It consists partlyhave different directions. It consists partly
of the fibers derived from the other facialof the fibers derived from the other facial
muscles which pass into the lips, partly ofmuscles which pass into the lips, partly of
fibers proper to them.fibers proper to them.
 Of the former there is no. of them derivedOf the former there is no. of them derived
from buccinator, and from the deeperfrom buccinator, and from the deeper
stratum.stratum. www.indiandentalacademy.comwww.indiandentalacademy.com

 Some of the buccinator fibers viz: thoseSome of the buccinator fibers viz: those
near the middle of the muscle- decussate atnear the middle of the muscle- decussate at
the angle of the mouth; the uppermost andthe angle of the mouth; the uppermost and
the lowermost fibers pass across the lipsthe lowermost fibers pass across the lips
from side to side without decussation.from side to side without decussation.
 Superficial to this is the second strata,Superficial to this is the second strata,
formed by the levator and the depressorformed by the levator and the depressor
anguli oris, which cross each other at theanguli oris, which cross each other at the
angle of the mouth; the fibers from theangle of the mouth; the fibers from the
levator pass to the lower lip and that fromlevator pass to the lower lip and that from
the depressor into the upper lip. Alongthe depressor into the upper lip. Along
which they run to reach the skin at thewhich they run to reach the skin at the
anterior median line.anterior median line.

 Fibers are also derived from the levator labiiFibers are also derived from the levator labii
superioris, zygomaticus major and minor, andsuperioris, zygomaticus major and minor, and
the depressor labii inferioris; these interminglethe depressor labii inferioris; these intermingle
with the transverse fibers described above, andwith the transverse fibers described above, and
have principally an oblique direction.have principally an oblique direction.
 Thus some eight or nine muscle thus convergeThus some eight or nine muscle thus converge
at the angle of the mouth and interlace here at aat the angle of the mouth and interlace here at a
palpable nodular mass ,palpable nodular mass , The modiulous.The modiulous. this canthis can
be fixed in a given position by the combinedbe fixed in a given position by the combined
action of the depressor anguli oris , zygomaticusaction of the depressor anguli oris , zygomaticus
major ,levator anguli oris.. This thus serves to fixmajor ,levator anguli oris.. This thus serves to fix
the attachments of the orbicularis oris and thethe attachments of the orbicularis oris and the
buccinator.buccinator.

 Within the lips the fibers of the orbicularisWithin the lips the fibers of the orbicularis
oris are divisible into two fasiculi, theoris are divisible into two fasiculi, the
marginal and the peripheral.marginal and the peripheral.
 These combine to form the labial bandsThese combine to form the labial bands
that are traceable to the modiulousthat are traceable to the modiulous
[lightoller 1925, burkitt and lightoller in[lightoller 1925, burkitt and lightoller in
1926, 1927]1926, 1927]
 The fibers of the lip are in obliqueThe fibers of the lip are in oblique
direction, and pass from the deep surfacedirection, and pass from the deep surface
of the skin to the mucous membrane, thruof the skin to the mucous membrane, thru
the thickness of the lip.the thickness of the lip.

 Finally there are fibers of the muscle bandsFinally there are fibers of the muscle bands
that are attached to the maxilla above andthat are attached to the maxilla above and
mandible below.mandible below.
 In the upper lip these constitute the incisiveIn the upper lip these constitute the incisive
labii superioris which arises from thelabii superioris which arises from the
alveolar border of the maxilla, opposite toalveolar border of the maxilla, opposite to
the lateral incisor tooth, and arching laterallythe lateral incisor tooth, and arching laterally
which is continuous with the other muscleswhich is continuous with the other muscles
at angle of the mouth.at angle of the mouth.

 The additional fibers of the lower lipThe additional fibers of the lower lip
constitute a slip of incisive labii inferioris, onconstitute a slip of incisive labii inferioris, on
each side; the slips arise from the mandible;each side; the slips arise from the mandible;
lateral to the mentalis, and mingles with thelateral to the mentalis, and mingles with the
other muscles at the angle of the mouth.other muscles at the angle of the mouth.
 In a study on children on fetal lips [14-25In a study on children on fetal lips [14-25
weeks] Latham and Deaton in 1976weeks] Latham and Deaton in 1976
conclude that orbicular oris fibers interlaceconclude that orbicular oris fibers interlace
and cross the midline to their cutaneousand cross the midline to their cutaneous
insertions, thus creating the ridges of theinsertions, thus creating the ridges of the
philtrum of the upper lip.philtrum of the upper lip.

 Nerve supply: - it is supplied by the lowerNerve supply: - it is supplied by the lower
buccal and the mandibular marginal branchbuccal and the mandibular marginal branch
of the facial nerve.of the facial nerve.
 Actions: - its ordinary action is to effectActions: - its ordinary action is to effect
direct closure of the lips, by its deep anddirect closure of the lips, by its deep and
oblique fibers it compresses the lips againstoblique fibers it compresses the lips against
the teeth.the teeth.
 The superficial part, consisting principally ofThe superficial part, consisting principally of
the decussating fibers , brings the lipsthe decussating fibers , brings the lips
together and protrudes them. Thetogether and protrudes them. The
orbicularis oris and other muscles of the lipsorbicularis oris and other muscles of the lips
play an important part in articulation, as wellplay an important part in articulation, as well
as in mastication. [Duckworth 1947]as in mastication. [Duckworth 1947]

The risorius: -The risorius: -
 Origin:-arises from the parotid fasciaOrigin:-arises from the parotid fascia
 Insertion:-is inserted into the skin at theInsertion:-is inserted into the skin at the
angle of the mouth.angle of the mouth.
 It is a narrow bundle of fibers, broad at itsIt is a narrow bundle of fibers, broad at its
origin.origin.
 It may vary much in its size and form; likeIt may vary much in its size and form; like
may arise from the zygomatic arch,may arise from the zygomatic arch,
external ear or the fascia over theexternal ear or the fascia over the
mastoid process.mastoid process.

 Nerve supply: - is supplied by the buccalNerve supply: - is supplied by the buccal
branches of the facial nerve.branches of the facial nerve.
 Action: - it retracts the angle of the mouthAction: - it retracts the angle of the mouth
and produces the sardonic expression.and produces the sardonic expression.
 Facial muscles also play an important roleFacial muscles also play an important role
in the speech and feeding and drinking.in the speech and feeding and drinking.
 Their importance in mastication hasTheir importance in mastication has
always been a topic of EMG study.always been a topic of EMG study.

Muscles of the
mastication:-

 These muscles immediately areThese muscles immediately are
concerned with the movements of theconcerned with the movements of the
mandible [and speech],mandible [and speech],
 These muscles are viz:-These muscles are viz:-
1.1. MasseterMasseter
2.2. TemporalisTemporalis
3.3. Pterygoid muscles.Pterygoid muscles.

The masseter: -The masseter: -
 A strong layer of fascia derived from the deep cervicalA strong layer of fascia derived from the deep cervical
fascia is named the parotid fascia; it covers thefascia is named the parotid fascia; it covers the
masseter and is firmly connected with it. It is attached tomasseter and is firmly connected with it. It is attached to
the lower border of the zygomatic arch and invests thethe lower border of the zygomatic arch and invests the
parotid glandparotid gland..

 It is quadrilateral in shape and consists of threeIt is quadrilateral in shape and consists of three
superimposed layers blending anteriorly.superimposed layers blending anteriorly.
 The superficial layer, the largest arises by a thickThe superficial layer, the largest arises by a thick
aponeurosis from the zygomatic process of theaponeurosis from the zygomatic process of the
maxilla and from the anterior 2/3rds of the lowermaxilla and from the anterior 2/3rds of the lower
border of the zygomatic arch.border of the zygomatic arch.
 Its fibers pass downwards and backwards, to beIts fibers pass downwards and backwards, to be
inserted into the angle and lower half of the lateralinserted into the angle and lower half of the lateral
surface of the ramus of the mandible.surface of the ramus of the mandible.
 Intramuscular septa in this region are responsibleIntramuscular septa in this region are responsible
for the ridge on the bone.for the ridge on the bone.

 The middle layer: - it arises from the deepThe middle layer: - it arises from the deep
surface of the anterior 2/3rd and thesurface of the anterior 2/3rd and the
posterior 1/3posterior 1/3rdrd
of the lower borderof the lower border
zygomatic arch.zygomatic arch.
 It is inserted in the middle of the ramus ofIt is inserted in the middle of the ramus of
the mandible.the mandible.
 The deep layer: - it arises from the deepThe deep layer: - it arises from the deep
surface of the zygomatic arch and issurface of the zygomatic arch and is
inserted into the upper part of the ramus ofinserted into the upper part of the ramus of
the mandible and the coronoid process.the mandible and the coronoid process.

 The middle and the deep layers constituteThe middle and the deep layers constitute
to form a cruciate muscle. [Where theto form a cruciate muscle. [Where the
fasiculi run in 2-3 directions]fasiculi run in 2-3 directions]
 As it is close to the skin it can be palpatedAs it is close to the skin it can be palpated
when it is thrown into contractionwhen it is thrown into contraction
vigorously as in clenching of the teeth.vigorously as in clenching of the teeth.
 Acc. To mcconnaill 1975 the mostAcc. To mcconnaill 1975 the most
superficial fibers are continuous thru theirsuperficial fibers are continuous thru their
attachment at the lower border of theattachment at the lower border of the
mandible, into the attachment of the medialmandible, into the attachment of the medial
pterygoid muscle.pterygoid muscle.

 Nerve supply: - is supplied by the branchNerve supply: - is supplied by the branch
of the anterior trunk of the mandibularof the anterior trunk of the mandibular
nervenerve
 Actions: - it elevates the mandible toActions: - it elevates the mandible to
occlude the teeth in mastication. Itsocclude the teeth in mastication. Its
activity in the resting position of theactivity in the resting position of the
mandible is minimal.mandible is minimal.
 In clenching of the teeth.In clenching of the teeth.
 It has little effect in side to sideIt has little effect in side to side
movements, protraction and the retractionmovements, protraction and the retraction
of the mandible.of the mandible. www.indiandentalacademy.comwww.indiandentalacademy.com

The temporal fascia:-The temporal fascia:-
 It covers the temporalis muscle. It is a strong,It covers the temporalis muscle. It is a strong,
fibrous investment covered, laterally, by thefibrous investment covered, laterally, by the
auricularis anterior and superior, the galeaauricularis anterior and superior, the galea
aponeurotica and part of the orbicularisaponeurotica and part of the orbicularis
oculi.The superficial temporal vessels and theoculi.The superficial temporal vessels and the
auriculotemporal nerve ascend over it.auriculotemporal nerve ascend over it.
 Above it is a single layer attached to the wholeAbove it is a single layer attached to the whole
of the sup. Temporal line and below it is twoof the sup. Temporal line and below it is two
layers one attached to the lateral and the otherlayers one attached to the lateral and the other
to the medial margin of the upper zygomaticto the medial margin of the upper zygomatic
arch.arch. www.indiandentalacademy.comwww.indiandentalacademy.com

 A small quantity of fat, the zygomaticA small quantity of fat, the zygomatic
branch of the superficial temporalbranch of the superficial temporal
artery, the zygomatico temporalartery, the zygomatico temporal
branch of the maxillary nerve liebranch of the maxillary nerve lie
between these layers.between these layers.
 The deep surface of the fascia affordsThe deep surface of the fascia affords
attachment to the superficial fibers ofattachment to the superficial fibers of
the temporalis.the temporalis.

The temporalis: -The temporalis: -
 Origin:-It is a fan- shaped muscle. It arises fromOrigin:-It is a fan- shaped muscle. It arises from
the whole of the temporal fossa [except the partthe whole of the temporal fossa [except the part
formed by the zygomatic arch] and the deepformed by the zygomatic arch] and the deep
surface of the temporal fascia.surface of the temporal fascia.

 Insertion:-Its fibers converge and descend into aInsertion:-Its fibers converge and descend into a
tendon which passes thru the gap between thetendon which passes thru the gap between the
zygomatic arch and the side of the skull, to bezygomatic arch and the side of the skull, to be
attached to the medial surface, apex, anteriorattached to the medial surface, apex, anterior
and posterior borders of the coronoid process,and posterior borders of the coronoid process,
and the anterior border of the ramus of theand the anterior border of the ramus of the
mandible nearly as far as the last molar tooth.mandible nearly as far as the last molar tooth.
 Nerve supply: - supplied by the deep temporalNerve supply: - supplied by the deep temporal
branch of the ant. Trunk of the mandibularbranch of the ant. Trunk of the mandibular
nerve.nerve.
 Actions: - it elevates the mandible i.e. closes theActions: - it elevates the mandible i.e. closes the
mouth and approximates the teeth.mouth and approximates the teeth.
 It is also contributor to the side to side grindingIt is also contributor to the side to side grinding
movements.movements.

 About its action on the elevation of theAbout its action on the elevation of the
mandible there are lots of studies thatmandible there are lots of studies that
states the temporalis is active in thestates the temporalis is active in the
forcible elevation but not involved inforcible elevation but not involved in
the slow elevation without occlusion.the slow elevation without occlusion.
[Vitti and basmajian 1977][Vitti and basmajian 1977]
 It’s not easy to palpate but theIt’s not easy to palpate but the
contraction of the temporalis musclecontraction of the temporalis muscle
can be felt.can be felt.

The lateral pterygoid: -The lateral pterygoid: -
 It is a short and thick muscle with twoIt is a short and thick muscle with two
parts of the head:-parts of the head:-

1.1. Upper from the infra temporal surfaceUpper from the infra temporal surface
and from the infra temporal crest of theand from the infra temporal crest of the
greater wing of sphenoid bone,greater wing of sphenoid bone,
2.2. Lower head from the lateral surface ofLower head from the lateral surface of
the lateral pterygoid plate.the lateral pterygoid plate.
 Insertion:-its fibers pass backwards andInsertion:-its fibers pass backwards and
laterally to be inserted in the depressionlaterally to be inserted in the depression
on the front of the neck of the mandible,on the front of the neck of the mandible,
and into the articular capsule and diskand into the articular capsule and disk
of the TMJ.of the TMJ.

 In the 3rd month of the I.U life the lateralIn the 3rd month of the I.U life the lateral
pterygoid muscle is inserted in thepterygoid muscle is inserted in the
mesenchyme condensed around the dev.mesenchyme condensed around the dev.
Condyle of the mandible but a part of itsCondyle of the mandible but a part of its
tendon sweeps backwards above thetendon sweeps backwards above the
condyle and gains into the portion of thecondyle and gains into the portion of the
meckels cartilage which later forms themeckels cartilage which later forms the
head of the malleus.head of the malleus.
 Then gets inserted into the articular disk ofThen gets inserted into the articular disk of
the TMJ and the attachment with thethe TMJ and the attachment with the
malleus does not persist.malleus does not persist.

 Nerve supply: - it is supplied by the br.Nerve supply: - it is supplied by the br.
from the anterior trunk of the mandibularfrom the anterior trunk of the mandibular
nerve.nerve.
 Actions: - it assists in opening the mouthActions: - it assists in opening the mouth
by pulling forward the condylar process ofby pulling forward the condylar process of
the mandible and the articular disk whilethe mandible and the articular disk while
the head of the condyle rotates on thethe head of the condyle rotates on the
articular disk. [Posselt 1952]articular disk. [Posselt 1952]

 In the closure the backward gliding of theIn the closure the backward gliding of the
articular disk and the condyle of thearticular disk and the condyle of the
mandible is controlled by the slowmandible is controlled by the slow
elongation of the lateral pterygoid, whileelongation of the lateral pterygoid, while
the masseter and the temporalis restorethe masseter and the temporalis restore
the jaw to the occlusal positionthe jaw to the occlusal position
 Along with the medial pterygoid of theAlong with the medial pterygoid of the
same side the lateral pterygoid advancessame side the lateral pterygoid advances
the condyle of that side so that the jawthe condyle of that side so that the jaw
rotates about the vertical axis.rotates about the vertical axis.

 When the medial and the lateral pterygoid actWhen the medial and the lateral pterygoid act
together than the mandible protrudes so that thetogether than the mandible protrudes so that the
lower incisors project in front of the upper andlower incisors project in front of the upper and
they also produce the side to side movement asthey also produce the side to side movement as
in chewing when the two muscles contractin chewing when the two muscles contract
alternatetly.alternatetly.
 According to [McNamara 1972—EMG study]According to [McNamara 1972—EMG study]
both the heads of the lateral pterygoid haveboth the heads of the lateral pterygoid have
diff. actions i.e. the upper head is being involveddiff. actions i.e. the upper head is being involved
in the chewing and the lower head is inin the chewing and the lower head is in
protrusion.protrusion.

The medial pterygoid: -The medial pterygoid: -
 It is quadrilateral in shape and consists of twoIt is quadrilateral in shape and consists of two
headsheads
 Deep head:-attaches to the medial surface ofDeep head:-attaches to the medial surface of
the lateral pterygoid plate and the groovedthe lateral pterygoid plate and the grooved
surface of the pyramidal process of thesurface of the pyramidal process of the
palatine bonepalatine bone
 superficial head:- from the lateral surfaces ofsuperficial head:- from the lateral surfaces of
the pyramidal processes of the palatine bonethe pyramidal processes of the palatine bone
and the tuberosity of the maxilla.and the tuberosity of the maxilla.

 Insertion:-its fibers pass downwards andInsertion:-its fibers pass downwards and
backwards and are attached to a strongbackwards and are attached to a strong
tendinous lamina, to the posterior-inferiortendinous lamina, to the posterior-inferior
part of the medial surface of the ramus andpart of the medial surface of the ramus and
the angle of the mandible, as high as thethe angle of the mandible, as high as the
mandibular foramen and nearly as forwardmandibular foramen and nearly as forward
as the mylohyoid groove.as the mylohyoid groove.

 Nerve supply:-it is supplied by theNerve supply:-it is supplied by the
branch of the mandibular nerve.branch of the mandibular nerve.
 Acc. to a study done by SchumacherAcc. to a study done by Schumacher
et.Al on the ramifications of theet.Al on the ramifications of the
muscular nerve of the masticatorymuscular nerve of the masticatory
muscles a very similar mode ofmuscles a very similar mode of
branching in all these muscles isbranching in all these muscles is
observed.observed.

 Actions: - it assists in elevating theActions: - it assists in elevating the
mandible. Acting with lateral pterygoid itmandible. Acting with lateral pterygoid it
protrudes the mandible.protrudes the mandible.
 When the 2 pterygoid of one side are inWhen the 2 pterygoid of one side are in
action the corresponding side is swungaction the corresponding side is swung
forward and to the opposite side with slightforward and to the opposite side with slight
degree of rotation.degree of rotation.

Palpation of muscles:-Palpation of muscles:-
 The muscles of mastication are palpated forThe muscles of mastication are palpated for
tenderness or pain during the screeningtenderness or pain during the screening
examination.examination.
 It is accomplished mainly by the palmar surfaceIt is accomplished mainly by the palmar surface
of the middle finger, with the index finger and theof the middle finger, with the index finger and the
forefinger testing the adjacent areas.forefinger testing the adjacent areas.
 Soft but firm pressure is applied to theSoft but firm pressure is applied to the
designated muscles, the fingers compresses thedesignated muscles, the fingers compresses the
adjacent tissues in a small circular motion.adjacent tissues in a small circular motion.

 A single firm thrust of 1 or 2 seconds isA single firm thrust of 1 or 2 seconds is
usually better than many light thrusts.usually better than many light thrusts.
 During that the patient is asked for theDuring that the patient is asked for the
symptoms.symptoms.
 The temporalis: -The temporalis: - it has three functionalit has three functional
areas and each is independently palpated.areas and each is independently palpated.
 Anterior region: - palpated above theAnterior region: - palpated above the
zygomatic arch and anterior to the TMJ.zygomatic arch and anterior to the TMJ.
 Middle region: - directly above TMJ andMiddle region: - directly above TMJ and
superior to the zygomatic arch.superior to the zygomatic arch.

 Posterior region: - palpated above and behindPosterior region: - palpated above and behind
the ear. Otherwise, the patient is asked to clenchthe ear. Otherwise, the patient is asked to clench
the teeth so that the temporalis contracts andthe teeth so that the temporalis contracts and
this is felt with hands placed on the abovethis is felt with hands placed on the above
specified locations.specified locations.
 The masseter musclesThe masseter muscles are palpated bilaterally atare palpated bilaterally at
their superior and inferior attachments.their superior and inferior attachments.
 The fingers are placed on the zygomatic archesThe fingers are placed on the zygomatic arches
and then dropped down slightly just anterior toand then dropped down slightly just anterior to
the tmj for palpating superior part.the tmj for palpating superior part.
 Secondly, the fingers are placed on the inferiorSecondly, the fingers are placed on the inferior
border of the rami to palpate inferior attachment.border of the rami to palpate inferior attachment.

 Medial pterygoid: -Medial pterygoid: - palpated at thepalpated at the
intersection of medial surfaces ofintersection of medial surfaces of
mandibular angles. Finger tips are placedmandibular angles. Finger tips are placed
on the inferior border of the mandible aton the inferior border of the mandible at
the angles and are rolled medially andthe angles and are rolled medially and
superiorly. Ask the patient to clench thesuperiorly. Ask the patient to clench the
teeth if it is difficult to locate the muscle.teeth if it is difficult to locate the muscle.

 The lateral pterygoid palpation is difficult.The lateral pterygoid palpation is difficult.
 It is accomplished by placing the forefingerIt is accomplished by placing the forefinger
behind the maxillary tuberosity, right abovebehind the maxillary tuberosity, right above
the occlusal plane, with the palmar surfacethe occlusal plane, with the palmar surface
of the finger directed medially toward theof the finger directed medially toward the
pterygoid hamulus.pterygoid hamulus.
 If there is tenderness in the superior head ofIf there is tenderness in the superior head of
the lateral pterygoid muscle than it indicatesthe lateral pterygoid muscle than it indicates
abnormal functional loading of the joint.abnormal functional loading of the joint.

 The finding are classified into fourThe finding are classified into four
categories.-categories.-
1. Zero: - no tenderness or pain is reported1. Zero: - no tenderness or pain is reported
by the patient,by the patient,
2. One: - patient’s response is recorded.2. One: - patient’s response is recorded.
Here the palpations cause discomfort.Here the palpations cause discomfort.
3. Two:-there is definite discomfort or pain.3. Two:-there is definite discomfort or pain.
4. Three: - patient shows evasive action4. Three: - patient shows evasive action
or verbally expresses desire not toor verbally expresses desire not to
palpate.palpate.

The accessory muscles ofThe accessory muscles of
facial expression:-facial expression:-
The superficial and the lateralThe superficial and the lateral
cervical muscles:-cervical muscles:-
 These include viz:-These include viz:-
1.1. The platysmaThe platysma
2.2. The trapeziusThe trapezius
3.3. The sterocleidomastoid musclesThe sterocleidomastoid muscles

The platysma: -The platysma: -
 Origin:-it is a broad sheet arising form theOrigin:-it is a broad sheet arising form the
fascia covering the upper part of the pectoralisfascia covering the upper part of the pectoralis
major and the deltoid.major and the deltoid.
 Insertion:-it is inserted at the lower border of theInsertion:-it is inserted at the lower border of the
body of the mandible and the posterior fibersbody of the mandible and the posterior fibers
cross the mandible and the lower anterior partcross the mandible and the lower anterior part
of masseter to be attached to the skin and theof masseter to be attached to the skin and the
subcutaneous tissue of the lower part of thesubcutaneous tissue of the lower part of the
face. And many fibers blending at the angle andface. And many fibers blending at the angle and
the lower part of the mouth.the lower part of the mouth.www.indiandentalacademy.comwww.indiandentalacademy.com

 Action: - when the entire platysma is inAction: - when the entire platysma is in
action it diminishes the concavityaction it diminishes the concavity
between the jaw and the side of thebetween the jaw and the side of the
neck.neck.

 Its anterior portion i.e. the thickest partIts anterior portion i.e. the thickest part
helps in depressing the mandiblehelps in depressing the mandible
 It also serves to draw down the lower lipIt also serves to draw down the lower lip
and the angle of the mouth as inand the angle of the mouth as in
expression of horror or surprise.expression of horror or surprise.
 The trapezius and the sterocleidomastoidThe trapezius and the sterocleidomastoid
maintain the posture of the head.maintain the posture of the head.

The accessory muscles.The accessory muscles.
 These are the muscle’s which whenThese are the muscle’s which when
involved assist the main group ofinvolved assist the main group of
muscles in the function ofmuscles in the function of
stomatoganthic function:stomatoganthic function:
1.1. The suprahyoid musclesThe suprahyoid muscles
2.2. The infra hyoid musclesThe infra hyoid muscles

The suprahyoid muscles: -The suprahyoid muscles: -
1.1. The digastric .The digastric .
2.2. The stylohyoid.The stylohyoid.
3.3. The mylohyoid .The mylohyoid .
4.4. The geniohyoid.The geniohyoid.

The digastric: -The digastric: -
 It has two bellies that are united by anIt has two bellies that are united by an
intermediate tendon. Hence the name.intermediate tendon. Hence the name.
 The posterior belly: - it s longer than theThe posterior belly: - it s longer than the
anterior and is attached to the mastoidanterior and is attached to the mastoid
notch of the temporal bone and passesnotch of the temporal bone and passes
downwards and forwards.downwards and forwards.

The anterior belly: - it is attached to theThe anterior belly: - it is attached to the
digastric fossa on the base of the mandibledigastric fossa on the base of the mandible
close to the median plane and passesclose to the median plane and passes
downward and backwards.downward and backwards.

 Actions: - it depresses the mandible and canActions: - it depresses the mandible and can
elevate the hyoid bone.elevate the hyoid bone.
 On EMG studies it has been confirmed thatOn EMG studies it has been confirmed that
they always act together and 2ndary to thethey always act together and 2ndary to the
lateral pterygoid for the depression thelateral pterygoid for the depression the
mandible and are required only during themandible and are required only during the
maximal depression. [Moyers 1950]maximal depression. [Moyers 1950]
 The posterior belly is active during theThe posterior belly is active during the
swallowing and the chewing.swallowing and the chewing.

The tongue:-The tongue:-
 The tongue begins itsThe tongue begins its
activities even beforeactivities even before
the birth when itthe birth when it
function thefunction the
swallowing ofswallowing of
amniotic fluid. It isamniotic fluid. It is
one of the best dev.one of the best dev.
Muscle / structure inMuscle / structure in
the human body atthe human body at
birth.birth.

Cranio facial musculature

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Cranio facial musculature