TMJ & JOINTS OF THE TMJ & JOINTS OF THE CRANIOFACIAL COMPLEXCRANIOFACIAL COMPLEX

Oral HistologyOral Histology

Dent 206Dent 206

JointsJoints

FunctionsFunctions MobilityMobility

Temporomandibular jointTemporomandibular joint Joints in the trunkJoints in the trunk Joints in the upper and lower limbsJoints in the upper and lower limbs

GrowthGrowth Craniofacial joints including TMJCraniofacial joints including TMJ

Craniofacial jointsCraniofacial joints Temporomandibular JointTemporomandibular Joint SynchondrosesSynchondroses Symphysis mentiSymphysis menti SuturesSutures

Simple suturesSimple sutures Serrated suturesSerrated sutures

Bone FormationBone Formation Endo-chondral ossificationEndo-chondral ossification

Base of the skullBase of the skull Nasal septumNasal septum Coronoid processCoronoid process Condylar processCondylar process

Intra-membranous ossificationIntra-membranous ossification Cranial vaultCranial vault Facial skeletonFacial skeleton Body of the mandibleBody of the mandible

Endo-chondral bone FormationEndo-chondral bone FormationDeposition of bone matrix on a pre-existing cartilage matrixDeposition of bone matrix on a pre-existing cartilage matrix

Mesenchymal tissueMesenchymal tissue CartilageCartilage BoneBone

The primary transitional cartilage is a hyaline cartilage whose shape resembles a small version of the bone to be formed

Intra-membranous Bone FormationIntra-membranous Bone FormationDirect mineralisation of matrix secreted by osteoblastsDirect mineralisation of matrix secreted by osteoblasts

Mesenchymal tissueMesenchymal tissue(Condensed)(Condensed)

BoneBone

Epiphyseal growthEpiphyseal growth

Endo-chondral ossification in a long boneEndo-chondral ossification in a long bone Intra-membranous bone collar forms Intra-membranous bone collar forms

within the perichondrium of the within the perichondrium of the cartilage modelcartilage model

Cartilage degeneration (by hypertrophy) Cartilage degeneration (by hypertrophy) and calcification starting at the central and calcification starting at the central portion of diaphysisportion of diaphysis

Blood vessels penetration bringing Blood vessels penetration bringing osteoblastsosteoblasts

Continuous primary bone deposited Continuous primary bone deposited over calcified cartilageover calcified cartilage

Calicified cartilage resorbed by giant Calicified cartilage resorbed by giant mutinucleated cellsmutinucleated cells

Primary ossification centerPrimary ossification center Secondary ossification centers at the Secondary ossification centers at the

epiphyses in a similar patternepiphyses in a similar pattern In secondary ossification centers In secondary ossification centers

cartilage remains in 2 regionscartilage remains in 2 regions The The articular cartilagearticular cartilage

Protection and mobilityProtection and mobility The The epiphyseal plateepiphyseal plate

Growth until closure at 20 ysGrowth until closure at 20 ys

Epiphyseal plateEpiphyseal plateHISTOLOGYHISTOLOGY

Histological zonesHistological zones Resting zoneResting zone

Proliferative zoneProliferative zone Chondrocytes divide to form parallel Chondrocytes divide to form parallel

columns (interstitial growth)columns (interstitial growth) Hypertrophic cartilage zoneHypertrophic cartilage zone

Large chondrocytes with cytoplasm filled Large chondrocytes with cytoplasm filled with glycogenwith glycogen

Calcified cartilage zoneCalcified cartilage zone Thin septa of cartilage become calcifiedThin septa of cartilage become calcified

Ossification zoneOssification zone Osteoblasts deposit primary bone over the Osteoblasts deposit primary bone over the

calcified cartialgecalcified cartialge

Temporomandibular JointTemporomandibular Joint FunctionsFunctions

Articulation between the mandible & the craniumArticulation between the mandible & the cranium Hinge with some some glidingHinge with some some gliding Growth of the mandibleGrowth of the mandible

Unique featuresUnique features Fibrous articular surface (not hyaline cartilage) Fibrous articular surface (not hyaline cartilage)

Reflects the intra-membranous development of the Reflects the intra-membranous development of the jointjoint

The intra-articular discThe intra-articular disc Upper joint cavityUpper joint cavity Lower joint cavityLower joint cavity

Two reciprocal jointsTwo reciprocal joints Bony ComponentsBony Components

Condylar processCondylar process Glenoid fossa of temporal boneGlenoid fossa of temporal bone Articular eminenceArticular eminence

Temporomandibular JointTemporomandibular Joint

Soft tissue Soft tissue componentscomponents Intra-articular discIntra-articular disc

Divides TMJ into 2 Divides TMJ into 2 joint cavitiesjoint cavities

Capsule - fibrousCapsule - fibrous LigamentsLigaments

Temporomandibular JointTemporomandibular Joint

Synovial jointSynovial joint Synovial membraneSynovial membrane

Lines the internal surface of the fibrous capsuleLines the internal surface of the fibrous capsule Lines the margins of the discLines the margins of the disc Does not cover the articular surfacesDoes not cover the articular surfaces Secrets the synovial fluidsSecrets the synovial fluids Consists of Consists of

a layer of flattened endothelial-like cell type, resting ona layer of flattened endothelial-like cell type, resting on a vascular layera vascular layer

Folded at rest & flattens out during movementFolded at rest & flattens out during movement Number of folded projections increase with ageNumber of folded projections increase with age

Synovial fluidsSynovial fluids LubricationLubrication NutritionNutrition

Temporomandibular JointTemporomandibular JointHISTOLOGYHISTOLOGY

Adult condyleAdult condyle Soft coveringSoft covering Calcified cartilageCalcified cartilage Compact BoneCompact Bone Cancellous boneCancellous bone

Glenoid fossa & eminenceGlenoid fossa & eminence Fibrous articular surfaceFibrous articular surface BoneBone

Intra-articular discIntra-articular disc Dense fibrous tissueDense fibrous tissue

Joint cavitiesJoint cavities

Layers covering the head of Layers covering the head of the adult’s bony condylethe adult’s bony condyle

Fibrous articular surface zoneFibrous articular surface zone Mainly collagenous although elastin are also Mainly collagenous although elastin are also

presentpresent In uppermost layers, fibers are parallel to In uppermost layers, fibers are parallel to

surfacesurface In deeper layer they run more verticallyIn deeper layer they run more vertically Articular surface covering the glenoid fossa Articular surface covering the glenoid fossa

& eminence is similar though thinner& eminence is similar though thinner Cellular-rich zoneCellular-rich zone

Proliferation zoneProliferation zone Fibrocartilaginous zoneFibrocartilaginous zone

fibrous layer with fibrous layer with remnants cartilage-like cellsremnants cartilage-like cells

Zone of calcified cartilageZone of calcified cartilage Remnants of secondary condylar cartilageRemnants of secondary condylar cartilage Different staining from that of boneDifferent staining from that of bone

TMJ of the childTMJ of the child

CondyleCondyle•Fibrous articular Fibrous articular surfacesurface•Proliferative zoneProliferative zone•ThickerThicker secondary secondary condylar cartilagecondylar cartilage•Ossification frontOssification front•Cancellous boneCancellous bone

Fibrous articular surfaceFibrous articular surface

Proliferative zoneProliferative zone

ThickerThicker secondary condylar secondary condylar cartilagecartilage

Ossification frontOssification front

Cancellous bone Cancellous bone (woven bone – mature bone)(woven bone – mature bone)

TMJ of the childTMJ of the child

Intra-articular discIntra-articular disc Dense collagenous fibrous tissueDense collagenous fibrous tissue Fibers run Fibers run

anteroposteriorly in the central regionanteroposteriorly in the central region transverse & superoinferior fibers may occurtransverse & superoinferior fibers may occur circumferentially at the peripherycircumferentially at the periphery crimped or wavycrimped or wavy

Type I collagen although type II & III may occurType I collagen although type II & III may occur Cells more at birthCells more at birth The bulk of the disc is avascularThe bulk of the disc is avascular

Derives nutrition from the synovial fluidsDerives nutrition from the synovial fluids Blood vessels at peripheryBlood vessels at periphery The superior lamella of the bilaminar zone has numerous blood The superior lamella of the bilaminar zone has numerous blood

vascular spaces which are filled with blood upon forward migration of vascular spaces which are filled with blood upon forward migration of condyle in jaw openingcondyle in jaw opening

Intra-articular discIntra-articular disc

SynchondrosesSynchondroses

Remnants of the primary chondocranial Remnants of the primary chondocranial cartilages after endo-chondral ossification of cartilages after endo-chondral ossification of cranial base bonescranial base bones

Fontanels/sutures are remnants of Fontanels/sutures are remnants of mesenchyamal tissues after intra-membranous mesenchyamal tissues after intra-membranous ossification of cranial vault and facial skeleton ossification of cranial vault and facial skeleton bonesbones

SynchondrosesSynchondrosesof the cranial baseof the cranial base

Spheno-occipitalSpheno-occipital Growth continues until Growth continues until

early teensearly teens

Spheno-ethmoidalSpheno-ethmoidal Replaced by fibrous tissue Replaced by fibrous tissue

shortly after birthshortly after birth

MidsphenoidalMidsphenoidal Active prenatallyActive prenatally Obliterated to form the Obliterated to form the

body of the sphenoid at body of the sphenoid at birth birth

SynchondrosisSynchondrosisHISTOLOGYHISTOLOGY

Inherent growth potentialInherent growth potential Bi-directional growth patternBi-directional growth pattern LayersLayers

Central resting zone Central resting zone Proliferative zone on either sidesProliferative zone on either sides Zone of hypertrophyZone of hypertrophy Replacement zoneReplacement zone

SuturesSutures Fontanels/sutures are remnants of Fontanels/sutures are remnants of

mesenchyamal tissues after intra-mesenchyamal tissues after intra-membranous ossification of cranial vault and membranous ossification of cranial vault and facial skeleton bonesfacial skeleton bones

LayersLayers Central zone (loose connective tissue)Central zone (loose connective tissue) Fibrous capsular zoneFibrous capsular zone Cambial zone (osteogenic zone)Cambial zone (osteogenic zone) BoneBone

Simple vs. serratedSimple vs. serrated Suture type vs.Suture type vs.

Growth potentialGrowth potential AgeAge

Types of suturesTypes of sutures

Symphysis MentiSymphysis Menti Symphysis mandibulae / Symphysis mentalisSymphysis mandibulae / Symphysis mentalis

The fibrocartilaginous union of the two halves of the mandible in The fibrocartilaginous union of the two halves of the mandible in the fetusthe fetus

It becomes an osseous union during the first yearIt becomes an osseous union during the first year Fibrocartilaginous tissueFibrocartilaginous tissue

CartilageCartilage Not derived from Meckel’s cartilage but differentiates from connective tissue Not derived from Meckel’s cartilage but differentiates from connective tissue

in the midlinein the midline At either sides of the centerAt either sides of the center

Fibrous tissueFibrous tissue At the centerAt the center

Mental ossiclesMental ossicles Develop at the end of 1Develop at the end of 1stst year year Fuse together and ossify the joint. Fuse together and ossify the joint.

Epiphyseal plate vs. condylar cartilageEpiphyseal plate vs. condylar cartilage

Epiphyseal plateEpiphyseal plate Condylar cartilageCondylar cartilage

Cartilage cells are in long columnsCartilage cells are in long columns Cartilage cells are scatteredCartilage cells are scattered

Cells hypertrophy with divisionCells hypertrophy with division Cells hypertrophy without divisionCells hypertrophy without division

Grows interstitiallyGrows interstitially Grows by apposition of cellsGrows by apposition of cells

Chondrocytes die eventuallyChondrocytes die eventually Chondrocytes still living in ossification frontChondrocytes still living in ossification front

Synchondrosis vs. epiphyseal plateSynchondrosis vs. epiphyseal plate

SynchondrosisSynchondrosis Epiphyseal plateEpiphyseal plate

A jointA joint Not a jointNot a joint

Two proliferation zonesTwo proliferation zones one proliferation zonesone proliferation zones

Bi-sided growthBi-sided growth Uni-sided growthUni-sided growth

Synchondrosis vs. Condylar cartilageSynchondrosis vs. Condylar cartilage

SynchondrosisSynchondrosis Condylar cartilageCondylar cartilage

Primary cartilagePrimary cartilage Secondary cartilageSecondary cartilage

Inherent growth potential in tissue cultureInherent growth potential in tissue culture Little intrinsic growth potential in tissue cultureLittle intrinsic growth potential in tissue culture

Proliferative zones on either side of centerProliferative zones on either side of center Undifferentiated fibroblast cells proliferate Undifferentiated fibroblast cells proliferate

Bi-sided growthBi-sided growth One-sided growth in more than one direction One-sided growth in more than one direction

Cartilage cells are in long columnsCartilage cells are in long columns Cartilage cells are scatteredCartilage cells are scattered

Cells die eventuallyCells die eventually Cells are still living at ossification frontCells are still living at ossification front

Cells hypertrophy with division Cells hypertrophy with division Cells hypertrophy without divisionCells hypertrophy without division

Grows interstitially (mitotic divisions)Grows interstitially (mitotic divisions) Grows by apposition of cellsGrows by apposition of cells

Considerable production of matrixConsiderable production of matrix Less production of matrixLess production of matrix