FUNCTIONAL ANATOMY OF TEMPOROMANDIBULAR JOINT

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FUNCTIONAL ANATOMY OF TEMPOROMANDIBULAR JOINT

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Title: FUNCTIONAL ANATOMY OF TEMPOROMANDIBULAR JOINT


1
FUNCTIONAL ANATOMY OF TEMPOROMANDIBULAR JOINT
2
TEMPOROMANDIBULAR JOINT
  • Two components
  • PASIF COMPONENTS
  • 1.Bone
    - Fossa mandibularis
    ossis temporalis - Capitulum
    mandibula ( condyle )
  • - Tuberculum articulare
  • ( articular eminence )

3
  • 2.Capsule and ligaments
  • 3.Articular disc
  • ACTIVE COMPONENTS
  • Masticator muscles
  • Masseter
  • Temporalis
  • Pterygoideus medialis
  • Pterygoideus lateralis
  • Additional muscles

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  • Considered as a ginglymoarthrodial joint
  • - hinging movement ginglymoid joint
  • - gliding movement arthrodial joint
  • It is formed by mandibular condyle fitting
    into mandibular fossa and the two bones is
    separated by articular disc
  • It is classified as a compound joint ( at
    least 3 bones ) functionally the articular disc
    served as a nonossified bone

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  • The TMJ is divided into superior and
    inferior cavity by the articular disc
  • Superior cavity
  • - Superior fossa mandibula
  • Inferior discus articularis
  • - Gliding action between condyle and
  • articular eminence
  • Inferior cavity
  • - Superior discus articularis
  • Inferior condyle
  • - Hinge action between undersurface of the
  • disc and the rotating surface of the
    condyle

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  • MANDIBULAR CONDYLE
  • Processus condyloideus
  • It is the posterior portion of the ramus
    mandibula that extends upward
  • Mediolateral 15 20 mm
  • Anteroposterior 8 10 mm
  • Anterior view medial and lateral poles,
  • the medial pole generally more prominent
  • The actual articulating surface extends
  • anteriorly and posteriorly to the most
    superior aspect ( P gt A )

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  • MANDIBULAR FOSSA
  • The squamous portion of the temporal bone (
    concave )
  • Anterior a convex bony prominence
  • ( tubercle ) articular eminence
  • Posterior squamotympanic fissure (M-L)
  • anteromedial petrosquamous fissure
  • posteromedial petrotympanic fissure

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  • - The posterior roof is thin not designed to
    sustain heavy force in which condyle situated
  • The articular eminence consists of thick dense
    bone to tolerate such forces
  • - The steepness of the articular eminence
    surface dictates the pathway of the condyle

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  • CAPSULE AND LIGAMENTS
  • 1.Capsula articularis capsular ligament
  • - It surrounds the entire TMJ
  • - Superior attachment the borders of the
  • articular surface of the mandibular fossa
  • and articular eminence
  • Inferior attachment collum mandibula
  • - Function
  • to resist any medial, lateral or inferior
  • forces that tend to separate or dislocate
    the
  • articular surface
  • to retain the synovial fluid

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  • 2.Collateral ( discal ) ligaments
  • - From medial and lateral borders of the disc to
    the poles of the condyle
  • the medial discal ligament
  • the lateral discal ligament
  • - Dividing the joint mediolaterally into
    superior and inferior joint cavities
  • - Composed of collagenous connective tissue
  • - Function
  • allow the disc move passively with the
    condyle
  • as it glides A - P

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  • permit the disc to be rotated A-P on
  • the articular surface of the condyle
  • These ligaments are responsible for the hinging
    movement between the condyle and the articular
    disc
  • - They have a vascular supply and are
    innervated

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  • 3.Temporomandibular ligament
  • - It lies at the lateral aspect of the
    capsular
  • ligament
  • - Composed of two parts
  • Outer oblique portion
  • From the outer surface of the articular
  • tubercle and zygomatic process postero
  • inferiorly to the outer surface of the
  • condylar neck it resists excessive
  • dropping of the condyle so limiting the
  • the extent of mouth opening

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  • Inner horizontal portion
  • From the outer surface of the
  • articular tubercle and zygomatic
  • process posteriorly and
    horizontally
  • to the lateral pole of the condyle
  • and posterior part of the articular
  • disc it limits posterior movement
  • of the condyle and disc

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  • 4.Sphenomandibular ligament
  • - It is an accesory ligament
  • - From the spine of the sphenoid bone and
  • extends downward to lingula mandibula
  • 5.Stylomandibular ligament
  • - The second accesory ligament
  • - From the styloid process and extends
  • downward and forward to the angle and
  • posterior border of the ramus mandibula
  • - It limits excessive protrusive movements
  • of the mandible

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  • ARTICULAR DISC
  • Composed of dense fibrous connective tissue
    devoid of any blood vessels or nerve fibers
  • Sagittal plane can be divided into 3 regions
    according to thickness
  • - anterior border
  • - posterior border slightly thicker than
  • anterior border
  • - central area is the thinnest intermediate
  • zone in which condyle is located normally

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  • Anterior view the disc is generally thicker
  • medially than laterally increased space
    between the condyle and the articular fossa
    toward the medial of the joint
  • The precise shape of the disc morphology of the
    condyle and mandibular fossa
  • - During movement the disc is somewhat flexible
    and can adapt to the functional demands of the
    articular surface do not imply that morphology
    of the disc is reversibly altered during movement

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  • The disc maintain its morphology unless
    destructive forces or structural changes occurs
    its morphology can be irreversibly altered
    biomechanical changes during function
  • RETRODISCAL TISSUE
  • The articular disc is attached posteriorly to
    this region
  • - It is a loose connective tissue region that
    highly vascularized and innervated

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  • Superior superior retrodiscal lamina
  • ( contains many elastic fibers ) bilaminary
    zone
  • It attaches the disc posteriorly to the
    tympanic plate
  • Inferior inferior retrodiscal lamina
  • ( composed chiefly collagenous fibers )
  • It attaches the inferior border of the
    posterior edge of the disc to the posterior
    margin of the articular surface of the condyle
  • - The remaining body of the tissue is attached
    posteriorly to a large venous plexus it fills
    with blood as the condyle moves forward

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  • Anterior region of the disc is attached to the
    capsular ligament
  • - Superior anterior margin of the articular
  • surface of the temporal bone
  • Inferior anterior margin of the articular
  • surface of the condyle
  • - Composed of collagenous fibers
  • Anteriorly the disc is also attached by
    tendinous fibers to the superior lateral
    pterygoid muscle

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  • The articular surface of the mandibular fossa
    and condyle are lined with dense fibrous
    connective tissue affords several advantages
    over hyaline cartilage
  • - less susceptible to the effects of aging
  • less likely to break down over time
  • - a better ability to repair
  • The internal surface of the joint cavity are
    surrounded by specialized endothelial cells that
    form a synovial lining produces synovial fluid
  • So TMJ a synovial joint

30
  • The synovial fluid serves two purposes
  • Acts as a medium for providing metabolic
    requirement, since the articular surfaces of the
    joint are nonvascular
  • As a lubricant during function
  • Two mechanisms of the lubrication
  • Boundary lubrication
  • Prevents friction in the moving joint
  • Weeping lubrication
  • Eliminates friction in the compressed but
    not moving joint

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MUSCLES OF MASTICATION
  • MASSETER
  • Rectangular muscle
  • There is two portions or heads ( caput )
  • Superficial head ( Caput superficial )
  • Origo - processus zygomaticus ossis
  • maxillae
  • - 2/3 ventral of the inferior border of
    the
  • zygomatic arch
  • Insertio extends downward and backward to
    the
  • tuberositas masseterica

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  • Profundus head ( Caput profundus )
  • Origo - 1/3 dorsal of the inferior border of
  • the zygomatic arch
  • - medial surface of the zygomatic
  • arch
  • Insertio extends downward and forward to
  • ramus mandibula and lateral
  • surface of processus coronoideus

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  • As fibers of the masseter contract mandible is
    elevated and the teeth are brought into contact
  • The superficial portion may also aid in
    protruding the mandible the deep portion
    stabilize the condyle against articular eminence

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  • TEMPORALIS
  • A fan-shaped muscle
  • Origo - temporal fossa
  • Its fibers extend downward between the
    zygomatic arch and the lateral surface of the
    skull
  • Insertio - processus coronoideus
  • - ramus mandibula

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  • Contraction of the muscle elevates the mandible
    and the teeth brought into contact
  • If only portions contract, the mandible is moved
    according to the direction of those fibers that
    are activated
  • According to fiber direction and ultimate
    function, it can be divided into 3 distinct areas

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  • Anterior portion
  • - The fibers are directed almost vertically
  • - Contraction mandible is raised
  • vertically
  • Middle portion
  • - The fibers run obliquely across the lateral
  • aspect of the skull ( forward as they pass
  • downward )
  • - Contraction elevate and retrude the
  • mandible

38
  • Posterior portion
  • -Run almost horizontally, coming forward
    above the ear to join other temporalis fibers as
    they pass under the zygomatic arch
  • -The function is somewhat controversial
  • causes elevation and only slight retrusion

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  • PTERYGOIDEUS MEDIALIS
  • Consists 2 heads ( caput )
  • Caput superficial
  • Origo - facies medialis lamina lateralis
  • processus pterygoideus ( fossa
  • pterygoideus )
  • - processus pyramidalis ossis
  • palatina
  • Caput profundus
  • Origo - processus pyramidalis ossis
  • palatina
  • - tuber maxillae

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  • Extend downward, backward and outward to
    insert along the medial surface of the mandibular
    angle (tuberositas pterygoidea)
  • - With the masseter, it forms a muscular sling
    support the mandible
  • - Contraction mandible is elevated and the
    teeth are brought into contact
  • - It is also active in protruding the mandible
  • - Unilateral contraction mediotrusive movement
    of the mandible

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  • PTERYGOIDEUS LATERALIS
  • It consists 2 heads or bellies with different
    function
  • Caput superior
  • Origo facies infratemporalis ala magna
  • ossis sphenoidalis,
  • extending almost horizontally,
    back
  • ward and outward to insert on the
  • articular capsule, the disc and
    the
  • neck of the condyle ( fovea
    pterygoid )

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  • Caput inferior
  • Origo - facies lateralis lamina lateralis
  • processus pterygoideus
  • extends backward, upward and outward to
  • insert on the neck of the condyle ( fovea
  • pterygoidea )

46
  • Function
  • The superior lateral pterygoid is active during
    power stroke closure mandible against
    resistance ( chewing and clenching )
  • While the inferior active during opening, the
    superior remains inactive, becoming active only
    in conjunction with the elevator
  • The right and left inferior contracts
    simultaneously the condyles are pulled down the
    articular eminence and the mandible is protruded
  • The inferior functions with the mandibular
    depressors the mandible is lowered and the
    condyles gide forward and downward on the
    articular eminences
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