Transcript 11. muscles of mastication2010-10

Temporal & infratemporal fossae
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Temporal fossa :extends
above by the sup.temporal
line and below by
zygomatic arch.
Infratemporal fossa : lies
beneath the base of the
skull, between the pharynx
(medially) & ramus of
mandible (laterally).
or the space lying below
the temporal fossa and
behind the maxilla.
Muscles of mastication: 1-Temporalis
It lies in the temporal fossa.
Origin :floor of temporal fossa
& temporal fascia.
Insertion :by a tendon into the
coronoid process of the mandible.
N.supply : deep temporal
nerves from the ant.division of
mandibular N.
Action : anterior fibers --elevate the mandible.
posterior fibers--- retract the
mandible.
Muscles of mastication
2-Masseter muscle :
Origin : lower border &
inner surface of zygomatic
arch.
Insertion : lateral (outer)
surface of ramus of the
mandible.
N.supply : masseteric N.
from anterior division of
mandibular N.
Action : raises the mandible.
Muscles of Mastication attached to
mandible :
Lateral Surface
Medial Surface
Contents of the temporal fossa
1-Temporalis muscle.
2-Temporal fascia---covers temporalis muscle,
attached above to sup.temporal
line and below to upper border
of zygomatic arch.
3-Deep temporal nerves :
from the ant. division of
mandibular N., emerge from
upper border of lateral
pterygoid, enter the deep
surface of temporalis .
Contents of the temporal fossa
4-Auriculotemporal
nerve : arise from the
posterior division of
mandibular N. It emerges from
upper border of parotid gland ,
It lies behind superficial
temporal artery & TMJ,
in front of the auricle.
It supplies skin of auricle ,
ext.auditory meatus and the
scalpe over the temporal region.
Contents of the temporal fossa
5-Superficial temporal
artery : it is a terminal
branch of ext.carotid artery.
It Emerges from upper
border of parotid gland,
behind T.M.J.
It crosses root of zygomatic
arch in front of auriculotemporal N. & auricle ,here
its pulsation can be easily felt.
Contents of Infratemporal fossa
Lateral & medial
pterygoid muscles
(muscles of mastication)
Branches of the
mandibular N.
Otic ganglion.
 Chorda tympani.
Maxillary artery.
Pterygoid venous plexus.
Lateral pterygoid
Origin :upper head---- from the
infratemporal surface of the greater wing of
sphenoid. Lower head---- from the lateral
surface of lateral pterygoid plate.
Insertion :neck of mandible (pterygoid
fovea) & articular disc of T.M.J.
N.supply :anterior division.of mandibular
N.
Action:
1-Pulls the neck of mandible forward with the
articular disc to depress mandible during
opening of mouth.
2-Acting with medial pterygoid of the same
side during movement of chewing.
3-Acting with medial pterygoid to protrude
the mandible.
Medial pterygoid
Origin : superficial head----from the tuberosity of the
maxilla. Deep head----- from
the medial surface of the lateral
pterygoid plate.
Insertion: angle of
mandible (medial surface).
N.supply : main trunk of
mandibular N.
Action :
1-elevates the mandible.
2-Acting with lateral pterygoid
during movement of chewing.
Tempromandibular joint (TMJ)
Articlation : between the
articular tubercle & mandibular
fossa of temporal bone, and the
head of mandible (condyloid
process).
Type :condyloid synovial
joint.
Capsule :it surrounds the
joint.
Synovial membrane--- lines
the capsule in upper & lower
cavities.
Ligaments of Temperomandibular
Lateral temporomandibular
joint :
ligament : lies on the lateral side
of joint ,between the tubercle and
lateral surface of the neck of
mandible.
Sphenomandibular ligament :
lies on the medial side of the joint
,it connects the spine of sphenoid
to the lingula of mandibular
foramen.
Stylomandibular ligament behind &
medial .to the joint. it is a band of
thickened deep cervical fascia,
from apex of styloid process to angle
of mandibule.
Intracapsular articular disc
It is a plate of fibro-cartilage,
it divides the joint into upper
& lower cavities.
It is attached in front to the
tendon of lat. pterygoid , and
by fibrous bands to head of
mandible.
Its upper surface is concavoconvex to fit the articular tubercle
& mandibular fossa , while
its lower surface is concave to fit
the head of mandible.
N.supply-auriculotemporal & masseteric branches of mandibular N.
Movements:
Depression of mandibule :
by lat.pterygoid, helped by
digastric, geniohyoid & mylohyoid
muscles.
Elevation :by temporalis,
masseter, and medial pterygoid.
Protrusion : by lateral +
medial pterygoids of both sides.
Retraction :by post.fibers of
temporalis .
Lateral chewing movement:
by lat.& med. Pterygoids of both sides
Relation of the Temporomandibular
joint (TMJ) :
Anteriorly : mandibular notch
and masseteric N. & artery
(structures passing through
mandibular notch).
Posteriorly : ext.auditory
meatus, glenoid process of
parotid gland., auriculotemporal
N., & superficial temporal artery.
Laterally :parotid gland, fascia
& skin.
Medially : maxillary vessels.
Clinical significance of the TMJ :
The great strength of the Lat.TM ligament
prevents head of mandible from passing backward
to cause fracture of the tympanic plate in case of
severe blow on the chin.
 The articular disc
may be partially detached
causing noisy & audible
click, during movements
of the joint.
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Dislocation of the TMJ
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Sometimes occurs when the
mandible is depressed.
In case of minor blow on chin or
sudden contraction of lateral
pterygoids as in yawning, leads to
pull the head of mandible &
articular disc forward beyond the
summit of tubercle.
Reduction of disloction : by
pressing the thumbs downward
on the lower molar teeth and
pushing the jaw backward.