MUSCLES OF MASTICATION & TEMPOROMANDIBULAR JOINT

TEMPORAL &
INFRATEMPORAL FOSSA
• 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).

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 .

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.

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 auriculo-
temporal 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.

INRODUCTION
MASTICATION is a process by which food is
made into small particles, this function is done
by muscles of mastication and temporo
mandibular joint.
There are 4 types of muscles of mastication
1 Temporalis
2 Masseter
3 Medial Pterygoid
4 Lateral Pterygoid.

TEMPORALIS
FAN SHAPED MUSCLE
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.

MASSETER MUSCLE
AKA CHEWER
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.

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

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

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
acting alternately.

WHAT IS TEMPOROMANDIBULAR
JOINT ??
The Temporomandibular joint or TMJ is a
complex, multiaxial, synovial, bicondylar
and ginglimodiarthroidial type of joint. It
is highly specialized unique joint and has
got many distinctive characteristics.

GINGLYMOID JOINT-HINGING MOVEMENTS
ARTHRODIAL JOINT –GLIDING MOVEMENTS

CONTENTS
• MANDIBULAR FOSSA
• ARTICULAR EMINENSE
• CONDYLE
• FIBROUS JOINT CAPSULE
• SEPERATING DISK
• LIGAMENTS

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
JOINT
Lateral temporomandibular
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 concavo-
convex to fit the articular tubercle
& mandibular fossa , while
its lower surface is
concave to fit the head of mandible.

NERVE SUPPLY
• auriculotemporal & masseteric branches of
MANDIBULAR NERVE
VASCULARISATION
Arterial Supply:
Branches of External Carotid Artery
1.Superficial temporal artery
2.Deep auricular artery
3.Anterior tympanic artery
4.Ascending pharyngeal artery
5.Maxillary artery
Venous Supply:
1.Venous plexus
2.MaxillarY vein
3.Transverse facial vein
4.Supericial temporal vein
NOTE : The blood supply of TMJ is only superficial i.e there is no
blood supply in the capsule. It takes its nourishment from Synovial
fluid.

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.

TEMPOROMANDIBULAR JOINT
DISORDERS
CLASSIFICATION
1. Intra-articular origin or inTrinsic disorders
2. Extra-articular origin or extrinsic disorders

DISORDERS DUE TO EXTRINSIC FACTORS
Masticatory muscle disorders:
a. Protective muscles splinting
b. Masticatory muscle spasm( MPD syndrome)
c. Masticatory muscle inflammation (myositis)
Problems that result from extrinsic trauma:
a. Traumatic arthiritis
b. Fracture
c. Internal disc derangement
d. Myositis, myospasm
e. Tendonitis
f. Contracture of elevator muscle

DISORDERS DUE TO INTRINSIC
FACTORS
1. Trauma
a. Dislocation, subluxation
b. Heamarthrosis
c. Intracapsular and extracapsular fracture
2. Internal disc displacememt
a. Anterior disc displacemet with reduction
b. Anterior disc displacement without reduction
3. Arthiritis
a. Osteoarthiritis
b. Rheumatoid arthiritis
c. Juvenile rheumatoid arthiritis
d. Infection arthiritis
4. Developmental defects
a. Condylar agenesis or aplasia
b. Bifid condyle
c. Condylar hyperplasia
5. Ankylosis
6. Neoplasms

DISLOCATION OF THE TMJ
• 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.

Imaging Features
 Anterior disc displacement: posterior band of the
disc located anterior to the superior portion of
the condyle at closed mouth on oblique sagittal
images
 Disc may have normal (biconcave) or deformed
morphology
 In opened mouth position disc may be in a
normal position (“with reduction”) or continue to
be displaced (“without reduction”)
Internal Derangements

lateral sections central sections open-mouth
Partial anterior disc displacement at baseline

Complete anterior disc displacement
Open-mouth MRIOpen-mouth MRImedial sectionmedial section AutopsyAutopsy

Lateral disc displacement and normal bone

Medial disc displacement
Oblique coronal MRIOblique coronal MRIcoronal MRIcoronal MRI

Osteoarthritis
Definition
Non-inflammatory focal degenerative disorder of
synovial joints, primarily affecting articular
cartilage and sub-condylar bone; initiated by
deterioration of articular soft-tissue cover and
exposure of bone.
Clinical Features
 Crepitation sounds from joint(s)
 Restricted or normal mouth opening capacity
 Pain or no pain from joint areas and/or of
mastication muscles
 Occasionally, joints may show inflammatory signs
 Women more frequent than men

Advanced osteoarthritis and anterior disc
displacement, with joint effusion

Rheumatoid arthritis. A MRI shows completely destroyed disc, replaced
by fibrous or vascular pannus and cortical punched-out erosion (arrow)
with sclerosis in condyle.

ANKYLOSIS
Definition
Fibrous or bony union between joint
components.

GROWTH DISTURBANCES
(ANOMALIES)
Definition
Abnormal growth of mandibular condyle; overgrowth,
undergrowth, or bifid appearance.

Normal TMJ
Condylar Hypoplasia
CONDYLAR HYPOPLASIA
AND FACIAL ASYMMETRY

Inflammatory or Tumor-like Conditions
Calcium Pyrophosphate Dehydrate Crystal
Deposition Disease (Pseudogout)

BENIGN TUMORS
Synovial Chondromatosis
• Benign tumor characterized by cartilaginous metaplasia of
synovial membrane, usually in knee, producing small
nodules of cartilage, which essentially separate from
membrane to become loose bodies that may ossify.

OSTEOCHONDROMA
Definition
Benign tumor characterized by normal bone and
cartilage, near growth zones.

Malignant Tumors
Osteosarcoma mandible; 18-yearold female

Malignant tumor, mandible; 70- year-old male
with metastasis from lung cancer

IMAGING
• PANORAMIC PROJECTION
• PLAIN FILM IMAGING
• CONVENTIONAL TOMOGRAPHY
• COMPUTED TOMOGRAPHY
• ARTHROGRAPHY
• MRI
• TRANSCRANIAL VIEW

MUSCLES OF MASTICATION & TEMPOROMANDIBULAR JOINT

MUSCLES OF MASTICATION & TEMPOROMANDIBULAR JOINT

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