epithelial tissues .pdf

Education

1. EPITHELIUM
PRESENTED BY:
DR. KALPAJYOTI BHATTACHARJEE
DEPT. OF ORAL PATHOLOGY AND MICROBIOLOGY

2. CONTENTS
Definition
Development
Characteristics
Classification
Functions
Cellpolarity
Membranespecializationofepithelia
Glands
Epithelialcellrenewal
Structureoftheoralepithelium

3. DEFINITION
Epitheliumisanavasculartissuecomposedofcellsthat
covertheexteriorbodysurfacesandlineinternalclosed
cavities(includingthevascularsystem)andbodytubes
thatcommunicatewiththeexterior(thealimentary,
respiratory,andgenitourinarytracts).Epitheliumalso
formsthesecretoryportion(parenchyma)ofglandsand
theirducts.Inaddition,specializedepithelialcellsfunction
asreceptorsforthespecialsenses(smell,taste,hearing,
andvision).

4. DEVELOPMENT
EPITHELIUM IS DERIVED FROM 3 GEREM LAYERS
ECTODERM
MESODERM
ENDODERM
ALTHOUGH MOST OF THE EPITHELIA ARE DERIVED
FROM ECTODERM AND ENDODEREM

6. ECTODERM:Oralandnasalmucosa,cornea,epidermis
oftheskin&glandsoftheskin&themammaryglands.
ENDODERM:Theliver,thepancreas&theliningofthe
respiratoryandGIT.
MESODERM:Uriniferoustubulesofthekidney,thelining
ofthemaleandfemalereproductivesystems,the
endothelialliningofthecirculatorysystemandthe
mesotheliumofthebodycavity.

8. CHARACTERISTICS
Theyarecloselyapposedandadheretooneanotherby
specializedcelljunctions.
Theyexhibitfunctionalandmorphologicpolaritythrough
afreesurfaceorapicaldomain,alateraldomain,anda
basaldomain.
Theirbasalsurfaceisattachedtoanunderlyingbasement
membrane.

11. EPITHELIALCELLSthatlackafreesurfaceareseen
in:
interstitialcellsofLeydiginthetestis
theluteincellsoftheovary
theparenchymaoftheadrenalgland
anteriorlobeofthepituitarygland
Epithelioreticularcellsofthethymus
certaintypesofinjury,Infectionsandtumors

12. EPITHELIUMcreatesaselectivebarrierbetweenthe
externalenvironmentandtheunderlyingconnective
tissueseenin
Blood
lymph

13. CLASSIFICATION
1)SIMPLE:
•Squamous
•cuboidal
•columnar
2)PSEUDOSTRATIFIED
3)STRATIFIED
•Squamousnonkeratinised
•Squamouskeratinised
•Cuboidal
•Columnar
•transitional

14. SIMPLE-Whenitisonecelllayerthick
STRATIFIED-Whenithastwoormorecelllayer.
SQUAMOUS-Whenthewidthofthecellisgreaterthan
itsheight.
CUBOIDAL-Whenthewidth,depth&heightare
approximatelythesame.
COLUMNAR-Whentheheightofthecell
approximatelyexceedsthewidth.

16. SIMPLESQUAMOUS EPITHELIUM
Composedofflattened,irregularlyshapedcells
formingacontinuoussurfacewhichmaybereffered
toaspavementedepithelium.
Term‘squamous’derivesfromthecomparisonofthe
cellstothescalesofafish.
Supportedbyanunderlyingdelicatemembrane.
Involvedinpassivetransportofeithergasesorfluids.

17. PRESENTIN:
Lining-pulmonaryalveoli,loopofHenle,parietallayerof
Bawmancapsule,innerandmiddleear,bloodand
lymphaticvessels,pleuralandperitonealcavities.
FUNCTION:
Limitingmembrane
Fluidtransport
Gaseousexchange
Lubrication
Reducingfriction
Liningmembrane

18. SIMPLE SQUAMOUS EPITHELIUM

19. SIMPLE CUBOIDAL EPITHELIUM
Intermediateformbetweensimplesquamousand
simplecolumnarepithelium.
Nucleusisroundandlocatedinthecentreofthecell.
Presentin:
Ductsofexocrineglands
Surfaceofovary
Kidneytubules
Thyroidfollicles

20. Functions:
Secretion
Absorption
Surface barrier

21. SIMPLE CUBOIDAL EPITHELIUM

22. SIMPLE COLUMNAR EPITHELIUM
Cellsaretallerandappearcolumnarinsectionsatright
anglestothebasementmembrane.
Nucleiareelongatedandmaybelocatedtowardsthe
base,thecentreoroccasionallytheapexofthe
cytoplasm,thisisknownaspolarity.
PRESENTIN:
Smallintestine&colon
Stomachliningandgastricglands
Gallbladder

23. FUNCTION:
Transportation
Absorption
Secretion
Protection

25. SIMPLECOLUMNAR CILIATEDEPITHELIUM
Describedasaspecialentitybecauseofthepresenceof
surfacespecialisationcalledcilia.
Eachciliaconsistsofafingerlikeprojectionofthe
plasmamembrane.
Notcommoninhumansexceptinthefemale
reproductivetract.

26. Simple columnar ciliated epithelium

27. GOBLETCELL
Thesearemodifiedcolumnarepithelialcellswhich
synthesizeandsecretemucin.
Scatteredamongthecellsofmanyepitheliallinings
particularlyrespiratoryandGIT.
MucuscontentstainforglycoproteinusingPAS.
Thepartofthecellwheresecretoryvesicle
accumulatesbulgesandcompresses the
neighboringcells.

29. PSEUDOSTRATIFIED COLUMNAR EPITHELIUM
Thetermpseudostratifiedisderivedfromtheappearance
ofthisepitheliuminsectionwhichconveystheerroneous
impressionthatthereismorethanonelayerofcells.
Truesimpleepitheliumsinceallthecellsrestonthe
basementmembrane.
Nucleiaredisposedatdifferentlevelsthuscreatingthe
illusionofcellularstratification.

30. Exhibitpolaritywithnucleiconfinedtothebasaltwo-third
oftheepithelium,ciliaareneverpresentonstratified
epithelium
PRESENTIN:
Trachea&bronchialtree
Ductusdeferens
Auditorytubeandtympaniccavity
Nasalcavity&lacrimalsac
Maleurethra
Largeexcretoryducts

31. FUNCTION:
Secretion
Absorption
Lubrication
Transportation
Protection

33. STRATIFIED SQUAMOUS EPITHELIUM
Itconsistsofavariablenumberofcellslayerwhich
exhibittransitionfromacuboidalbasallayertoa
flattenedsurface.
Basallayerdividecontinuously.
Welladaptedtowithstandabrasionsincelossof
surfacecellsdoesnotcompromisetheunderlying
tissue.
Nucleibecomeprogressivelycondensed(pyknotic)
andflattened,beforeultimatelydisintegrating.

34. STRATIFIED SQUAMOUS EPITHELIUM

35. STRATIFIED SQUAMOUS NONKERATINISED
EPITHELIUM
Flattened with nuclei.
Moist superficial cells are living.
PRESENT IN:
Mouth
Epiglottis
Esophagus
Vocal folds
Vagina
FUNCTION:
Protection
Secretion

37. STRATIFIED SQUAMOUS KERATINIZED
EPITHELIUM
Flattened without nuclei
Dry, superficial cells are dead.
Nuclei are lost.
PRESENT IN:
Epidermis of skin.
FUNCTION:
Protection.

39. STRATIFIED CUBOIDAL EPITHELIUM
Thin,stratifiedepitheliumwhichusuallyconsistsof
onlytwoorthreelayersofcuboidalorlowcolumnar
cells.
Notinvolvedinsignificantabsorptiveorsecretory
activity
PRESENT IN:
Ducts of sweat glands
Large ducts of exocrine glands
Anorectal junction

40. FUNCTION:
Absorption
Secretion

42. STRATIFIED COLUMNAR EPITHELIUM
PRESENT IN:
Conjunctiva of eye
Some large excretory ducts
Portions of male urethra
FUNCTION:
Secretion
Absorption
Protection

44. TRANSITIONAL EPITHELIUM
Formofstratifiedepithelium.
Highlyspecializedtoaccommodateagreatdegreeof
stretch.
Sonamedbecauseithassomefeatureswhichare
intermediate(transitional)betweenstratifiedcuboidaland
stratifiedsquamousepithelia.
Inrelaxedstate(contracted)state,transitionalepithelium
appeartobeabout4-5layersthick. basalcellsare
roughlycuboidal,theintermediatecellsarepolygonal,and
thesurfacecellsarelargeandroundedandmaycontain2
nuclei.

45. Inthestretchedstate,itappears2-3cellsthick(although
theactualnumberoflayersremainsconstant)andthe
intermediateandsurfacelayersareextremelyflattened.
PRESENTIN:
Urethra
Ureters
Bladders
Renalcalyces
FUNCTION:
Protection
Distensible

47. FUNCTIONS
1)Protectionofunderlyingtissueofthebodyfrom
abrasionandinjury
2)Transcellulartransportofmoleculesacross
epitheliallayers
3)Secretionofmucus,hormones,enzymesandso
forthfromvariousglands.

48. 4)Absorptionofmaterialsfromalumen
5)Controlofmovementofmaterialsbetweenbody
compartmentsviaselectivepermeabilityof
intracellularjunctionsbetweenepithelialcells.
6)Detectionofsensationsviatastebuds,retinaofthe
eyeandspecializedhaircellsintheear.

49. CELLPOLARITY
Thefreeorapicaldomainisalwaysdirectedtowardsthe
exteriorsurfaceorthelumenofanenclosedcavityortube.It
isrichinionchannel,carrierproteinandhydrolyticenzymes
aswellasaquaporins,channelformingproteinsthatfunction
inregulationofwaterbalance.
Lateraldomaincommunicateswithadjacentcells&is
characterizedbyspecializedattachmentareas.
Thebasaldomainrestsonthebasallaminaanchoringthe
celltounderlyingconnectivetissue.

51. MEMBRANE SPECIALIZATIONOFEPITHELIA
Theintercellular,luminalandbasalsurfaceofepithelial
cellsexhibitavarietyofspecialization.
1)INTERCELLULAR SURFACE:
Theapposedsurfaceofepithelialcellsarelinedby
severaldifferenttypesofmembraneandcytoskeletal
specialization.Celljunctionsare:
a)Occludingortightjunctions:
Locatedimmediatelybehindtheluminalsurfaceof
simplecolumnarepithelium
Intercellularspacesareoblitereted
Transmembraneadhesiveprotein-occludin,claudin,
junctionaladhesivemolecule

52. Eachtightjunctionformsacontinuous
circumferentialbandorzonulesaroundthecelland
arethusknownaszonulaoccludens.
FUNCTIONS:
Sealadjacentcellstogether
Involvedincellsignaling
Definesapicalandbasolateraldomainof
plasmamembrane.
Tightnessofthejunctionisrelatedtotheclaudins
present

55. b) Adhering junctions:
Tightlybindstheconstituentcellsoftheepithelium
togetherandactsasananchorage
Cytoskeletonofallthecellsareeffectivelylinkedintoa
singlefunctionalunit
Apoptosis,lossofcellpolarity,unregulatedcell
proliferationareabsent.
Importantincellularsignaling
Intercellularspace-20nm

57. CELL TO CELL ADHESIVE JUNCTION:
Transmembraneprotein–cadherin
Cytoplasmicadaptarprotein-catenin
Zonaadherens-e-cadherin
A&Bcatenins,nectins
actinfilaments
Maculaadherens-Adesmosome alsoknownasmacula
adherensisacellstructurespecializedforcell-to-
celladhesion.
Desmoglein&desmocollin
Desmoplakin,Plakoglobin,
Plakophollin
Intermediatefilaments

60. CELLTOCELLMATRIXJUNCTION:
Focaladhesionwhichanchoractinfilamentsofthe
cytoskeletonintothebasementmembrane
Integrin,A-actinin,vinculin,talin,actinfilaments,remodelling
ofactinfilaments.
Hemidesmosomes whichanchortheintermediatefilaments
ofthecytoskeletonintothebasementmembrane.
Hemidesmosomes areasymmetricalandarefoundin
epithelialcellsconnectingthebasalfaceofthecelltobasal
lamina.Similarinformtodesmosomeswhenvisualizedby
electronmicroscopy
Integrin,A6B4,BP230,Plectin,intermediatefilamentslinks
thecellstothebasallamina.

61. Hemidesmosomes

62. c)Gapjunction:
Circularintercellularcontactsareascontaininghundreds
oftinyporeswhichpermitpassageofsmallmolecules
betweenadjacentcells.
Intercellularspace-2-3nm
Transmembraneprotein-connexin(formaqueous
channels)
Function-:-
Createsa(nexus)adjacentcellconductbetweentwo
adjacentcellsforpassageofsmallionsand
informationalmicromolecules.

64. 2)LUMINALSURFACE:
Luminalsurfaceofepithelialcellsmayincorporate
3maintypesofspecialization:
a)cilia
b)microvilli
c)stereocilli

65. CILIA
Relativelylongmotilestructurewhichareresolvedby
lightmicroscopy
Theyarehairlikeextensionsoftheapicalplasma
membranecontaininganaxoneme,themicrotubule-
basedinternalstructure.
Ciliagivea“crew-cut”appearancetotheepithelial
surfacebasalbodies.

67. MOTILE CILIA
Activemovementduetothepresenceofmicrotubule
associatedproteins;rapidforwardmovementwithslow
recoverystroke(halfconetrajectory).
mostcommonlyfoundonepitheliawhichfunctionin
transportingsecretions.
presentonspermcellsasflagella;providesaforward
movementtothespermcell.
Motileciliaarecapableofmovingfluidandparticles
alongepithelialsurfaceseg.Tracheobronchialtreeand
oviduct.

68. PRIMARYCILIA
foundinalmostallcellsinthebody.
transmitsignalsfromextracellularspaceintothe
cell.
Noactivemovement;passivelybendduetoflow
offluid.
Function:chemosensors
osmosensors
mechanosensors.

69. NODAL CILIA
Structuresimilartoprimaryciliaexcepttheyhave
anabilityforactivetransport,activerotational
movement
Foundintheembryoduringgastrulationonthe
bilaminardiscneartheareaofprimitivenode.
Essentialindevelopingleft-rightasymmetryof
internalorgans.

70. MICROVILLI
Microvilliarefingerlikecytoplasmicprojectionsonthe
apicalsurfaceofmostepithelialcells.
Inintestinalabsorptivecellthissurfacestructure
wasoriginallycalledthestriatedborder;inthe
kidneytubulecells,itiscalledthebrushborder.
Cannotbeindividuallyresolvedwiththemicroscope
Internalstructurecontainacoreofactinfilamentthat
arecrosslinkedbyseveralactinbindingprotein
Increaseabsorptivecapacity

72. STREOCILIA
Stereociliaareunusuallylong,immotilemicrovilli.
Foundonlysinglyorinsmallnumberinoddsites
suchasthemalereproductivetracts.
ContainsezrinandA-actinin.
Treadmillingeffect-structurerenewalprocess

73. STREOCILLIA

74. 3) BASAL SURFACE
Theinterfacebetweenallepitheliaandunderlying
supportingstructuresismarkedbyanoncellular
structureknownasthebasementmembrane.
Itprovidesstructuralsupportforepitheliaand
constituteaselectivebarriertothepassageof
materialbetweenepitheliumandsupportingtissue.

75. Hemidesmosomesprovidesameanofanchorage
ofthecellsviaitscytoskeletontothebasement
membraneandunderlyingsupportingtissue
Consistsof3zones:
laminalucida
laminadensa
laminafibroreticularisorsublaminadensa

76. LAMINADENSA
Thelaminadensaisacomponentofthebasement
membranezonebetweentheepidermisanddermisof
theskin,andisanelectron-densezonebetween
thelaminalucidaanddermis.
Synthesizedbythebasalcellsoftheepidermis
Electrondensematrix50nmthickbetweentheepithelium
andtheadjacentconnectivetissue
Exhibitanetworkoffine,3-4nmfilamentscomposedof
laminins,atypeivcollagenmolecule(chicken-wire)and
proteoglycansandglycoprotein.

78. LAMINALUCIDA
Thelaminalucidaisacomponentofthebasement
membranewhichisfoundbetweentheepitheliumand
underlyingconnectivetissue.
Clearzone40nmthickthatattachthecellstothe
basallamina
Contain-collagentypexvii,integrins,lamininv
Anchoringfibrilsconsistsofcollagentypeviiattach
basallaminatoconnectivetissue.

79. GLANDS
Typicallyglandsareclassifiedinto:
1)Exocrineglandsdischargetheirsecretoryproductviaa
ductontoanepithelialsurface.Cellsofwhichare
composedofhighlyspecializedepithelialcells,the
internalstructureofthecellsreflectingthenatureofthe
secretoryproductandthemodeofsecretion.
Morphology:a)simple:single,unbranchedduct.
b)compound:branchedductsystem.
2)Endocrineglandsareductless.Secretetheirproduct
intotheconnectivetissuewheretheyentertheblood
streamtoreachthetargetcells.Theproductsof
endocrineglandsarecalledhormone.

82. Insomeepithelia,individualcellssecretea
substancethatdoesnotreachthebloodstreambut
ratheraffectsothercellswithinthesameepithelia.
Suchsecretoryactivityisreferredtoasparacrine.
Thesecretorymaterialreachesthetargetcellsby
diffusionthroughtheextracellularspaceor
immediatelysubjacentconnectivetissue.

84. Cellsofexocrineglandsexhibitdifferent
mechanismofsecretion:
Merocrinesecretion-involvestheprocessof
exocytosisandisthemostcommonformof
secretion,proteinareusuallythemajorsecretory
product
Apocrinesecretion-involvesdischargeoffree,
unbroken,membraneboundvesiclescontaining
secretoryproduct.Thisisanunusualmodeof
secretionandappearstolipidsecretoryproductsin
thebreastsandsomesweatglands

85. Holocrinesecretion-involvesdischargeofwhole
secretorycellswithsubsequentdisintegrationofthe
cellstoreleasethesecretoryproduct.Occurs
principallyonthesebaceousglands.

87. EPITHELIAL CELL RENEWAL
Thestratifiedsquamousepitheliumofskinisreplacedin
approximately28days.
Cellsinthestratumbasaleundergomitosistoprovide
forcellrenewal.
Asthesecellsdifferentiatetheyarepushedtowardthe
surfacebynewcellsinthebasallayer.
Ultimately,thecellsbecomekeratinizedandsloughoff.

88. Thusasteadystateismaintainedwithinthe
epithelium,withnewcellsnormallyreplacing
exfoliatedcellsatthesamerate.
Cellsarisingbydivisioninthebasallayermay
remainintheprogenitorcellpopulationorundergoa
processofmaturationastheymovetosurface.

89. EPITHELIAL METAPLASIA
Epithelialmetaplasiaisareversibleconversionof
onematureepithelialcelltypetoanothermature
epithelialcelltype.
Metaplasiaisgenerallyanadaptiveresponseto
stress,chronicinflammation,orotherabnormal
stimuli.

90. EPITHELIAL METAPLASIA

91. TUMOURS ARISING FROM EPITHELIA
Atumourcanarisefromanytissueifthereisuncontrolled
growthofcells.
Amalignanttumourarisingfromanepitheliaisa
carcinoma.
Ifitarisesfromsquamousepitheliumitisasquamouscell
carcinoma
Iftumourarisingfromglandularepitheliumitiscalled
adenoma.
DiagnosiscanbemadebyImmunohistochemical
technique.

92. STRUCTUREOFTHEORALEPITHELIUM
Stratifiedsquamousvariety.
Maybekeratinized(orthoorparakeratinized)or
nonkeratinizeddependingonlocation.
Keratinized:gingivaandhardpalate(masticatory
mocosa).Inmanygingivalepitheliumisparakeratinized.
Nonkeratinized:cheeks,faucialandsublingualtissue.
Bothkeratinizedandnonkeratinizedcontains2groupsof
cells-keratinocytesandnonkeratinocytes.

93. TURNOVER TIME OF THE EPITHELIUM
Turnover time-time taken for a cell to divide and
pass through the entire epithelium.
E.g. –* skin -52 to 75 days .
* gut -4 to 14 days.
* gingiva -41 to 57 days.
* cheek -25 days.
Nonkeratinised buccal epithelium turns over faster
than keratinized gingival epithelium.

94. Keratinizedepithelium:
1)stratumbasale
2)stratumspinosum
3)stratumgranulosum
4)stratumcorneum

95. STRATUM BASALE
Singlelayerofcuboidalcells
MadeupofcellsthatsynthesizeDNAandundergo
mitosisthusprovidingnewcells
Basalcellsandparabasalcellsarereferredtoas
stratumgerminativumbutonlybasalcellscan
divide.
Basalcellssynthesizeproteins

96. Hemidesmosomesarefoundinbasallayer.
Lateralbordersoftheadjacentcellsareclosely
apposedandconnectedbydesmosomes.
Thebasalcellscontaintonofilamentsandare
attachedtotheattachmentplaque
Desmosomesconsistsof2principalproteins:
transmembranousproteinandproteinswithinthe
cellsandrelatedtoattachmentplaque.

97. STRATUM BASALE

98. STRATUM SPINOSUM
Irregularpolyhedralcellslargerthanbasalcells.
Inlightmicroscopy,itappearsthesearejoinedby
“intercellularbridges”
Tonofilamentsseemstocoursefromcelltocell
acrossthebridge.
Electronmicroscopyrevels-intercellularbridgesare
desmosomes andtonofibrilsarebundlesof
tonofilament.

99. Desmosome attachmentplaquescontainthe
polypeptidesdesmoplakinandplakoglobin.
Intercellularspace containsglycoprotein,
glycosaminoglycanandfibronectin.
Pricklecelllayer-shrinksawayfromeachother
remainingincontactatthedesmosomes.
Mostactivelayerinproteinsynthesis.

100. STRATUM SPINOSUM

101. STRATUM GRANULOSUM
Flatterandwidercellslargerthanspinouscells
Containsbasophilickeratohyalingranules
Nucleusshowdegerationandpyknosis.
Tonofilamentsaremoredenseinquantityandareoften
seenassociatedwithkeratohyalingranules.
Cellsurfacearemoreregularandmoreclosely
attachedtoadjacentcellsurface.

102. Lamellargranules:
keratinosome orodlandbody-
membranecoatingactsaspermeabilitybarrier.
Involucrin(keratolin)-proteinpresentat
theupperhalf.
Membranecoatinggranulesareglycoprotein.

103. STRATUM GRANULOSUM

104. STRATUM CORNEUM
keratinizedsquamaewhicharelargerandflatterthan
granularcells.
Nucleiandorganelleshavedisappeared.
Acidophilicandhistologicallyamorphouslayer.
Keratohyalingranuleshavedisappeared.
Cellsarecomposedofdenselypackedfilamentscoated
bybasicproteinofkeratohyalinegranules,filaggrin.

105. STRATUM CORNEUM

106. Orthokeratinizedepithelium:
donotcontainnuclei.
Parakeratinizedepithelium:
thestratumcorneumretainspyknoticnuclei.
Incompleteremovaloftheorganellesfromthe
cellsofthegranularlayeroccursothatthenuclei
remainasshrunkenpyknoticstructure,and
remnantsofotherorganellesalsomaybe
presentinthekeratinizedlayer

107. ORTHOKERATINISED EPITHELIUM

108. PARAKERATINIZED EPITHELIUM

109. NONKERATINIZED EPITHELIUM
Layers
Basal -(Stratum Basale)
Intermediate -(Stratum Intermedium)
Superficial -(Stratum Superficiale)

110. Basalcellsaresimilar.
Cellsofstratumintermediumarelargerthan
spinosumandareattachedbydesmosomesand
otherjunction.
Morecloselyattachedthanspinouscells.
NoStratumGranulosum

111. No Stratum Corneum.
Stratum Superficiale –nucleated cells
Less number of tonofilaments
Lack keratohyaline granules.

112. Havehigherrateofmitosisthankeratinized
epithelium.
Parakeratosis–physiologic
normally keratinizingtissue becomes
parakeratinized.
Keratosis-Pathologic
keratinizationoccursinanormallynonkeratinized
tissue.

113. KERATINOCYTE
Epidermal/epithelialcellsthatsynthesizekeratin.
Characteristicintermediatefilamentproteinis
cytokeratin.
Showcelldivision,undergomaturationandfinally
desquamate
Increaseinvolumeineachsuccessivefrombasalto
superficial.

114. NONKERATINOCYTES
Donotpossesscytokeratinfilament
Donotshowmitoticactivityundergomaturationand
finallydesquamate
Usuallydendriticandappearsunstainedorclearin
routineH&Estains
IdentifiedbyspecialstainorImunohistochemical
technique
Migratetooralepitheliumfromneuralcrestorbone
marrow.

115. MELANOCYTES
Presentinbasallayer.
Arisefromneuralcrestectoderm.
Stainingreaction-dopaoxidase-tyrosinase,silver
stains.
Stainedby:Mason-Fontanastain
Dendritic,nodesmosomesandtonofilaments.
Premelanosomesandmelanosomesarepresent.
Function-synthesisofmelaninpigmentgranules
(melanosomes) andtransfertosurrounding
keratinocytes.

117. LANGERHANS CELL
Presentinsuprabasallayer.
Arisefrombonemarrow.
Dendriticorclearcellswithnodesmosomesortonofilaments.
Characteristiclangerhansgranule-Birbeckgranules
Stainingreactions-cellsurfaceantigenmarkers
Stainsby:goldchloride,ATPase&immunofluorescent
markers.
Function-
antigentrappingandprocessing.

118. LANGERHANS CELL

120. MERKEL CELLS
Presentinbasallayer.
Arisefromdivisionofepithelialcell.
Stainingreaction-PASpositive.
Seeninmasticatorymucosabutareabsentinlining
mucosa
Non-dendriticwithlessdesmosomes and
tonofilaments.
sensoryandrespondtotouch.
Characteristicelectron-densevesiclesandassociated
nerveaxon.

121. MERKEL CELLS

122. ULTRASTRUCTURE OFEPITHELIALCELLS
Intracellularfilaments- tonofilaments
Intracellularproteins- cytokeratins
Lowmolwtkeratin(40)-glandular&simple
Intermediatewt- stratifiedepithelia
Highest(67)– keratinizedstratified
Stratifiedoralepithelim-keratin5&14
Keratinizedepithelium-keratin1,6,10,16
Non-keratinized -keratin4,13,19

123. REFERENCES
MichaelH.RossandWojciechPawlina;
HistologyAText&Atlas;6
th
edition;p.105-146
KumarGS,Orban’sOralHistologyand
Embryology,12
th
Ed,2009,Elsevier,NewDelhi,
p.210-226.
NanciA,TenCate’sOralHistologyDevelopment
structureandfunction,7
th
Ed,2008,Mosby,New
Delhi,p.320-336.

124. Singh.I,HistologyofHumanHistologyColourAtlas,5
th
Ed
,Jaypeebrothers,2009,NewDelhi,p.45-53.
Wheaters,functionalhistology,atextandcolouratlas,
4
th
edition,page80-96
BKBBerkovitz,oralanatomy,histologyandembryology,
3
rd
edition,page220-224
LeslicP.Gartner,colourtextbookofhistology,3
rd
edition,page85-109