FUNCTIONAL ANATOMY OF TEMPOROMANDIBULAR JOINT

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FUNCTIONAL ANATOMY OF TEMPOROMANDIBULAR JOINT
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TEMPOROMANDIBULAR JOINT

• Two components
• PASIF COMPONENTS
• 1.Bone
  - Fossa mandibularis
  ossis temporalis - Capitulum
  mandibula ( condyle )
  
• - Tuberculum articulare
• ( articular eminence )

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• 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

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• 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

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• 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 )

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• 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