oral mucosa seminar definition and characteristics

oral mucosa seminar contains 78 slides

3. By
Ahmed MostafaAhmed Mohamed Abbas
B.D.S, 2010 Faculty of Dental Medicine, Al-AzharUniversity
MDSc, 2018, in Oral and Dental Biology
Faculty of Dental Medicine -Al-AzharUniversity
Assistant lecturer, Oral Biology Department-Al-AzharUniversity

4. Objectives
I.Definition
II.Function
III.BoundariesoftheOralMucosa
IV.Classification
V.Histologicalstructure

5. I-Definition
Itisthemoistliningoftheoralcavity.
Itisstructurllyandfunctionallyatransitionalzone
betweentheskinandmucosaofGIT.
Atthelipsitiscontinuouswiththeskinandatthe
pharynxitiscontinuouswiththemoistmucosawhich
liningtherestofthegut.

6. Itshowssomeofthepropertiesofeach:-
Itresemblestheskinin:
•It possesses a stratified epithelium which is
keratinized in many places.
•It limits diffusion across it in both directions.
ItresemblestheGITin:
•It is constantly bathed in fluid.
•Its epithelial cells have high rate of turn over.

7. II-Function
1-Protection.
2-Sensation.
3-Secretion.
4-Thermal regulation.
5-Permeability and absorption.

8. 1-Protection
Theoralmucosaseparatesandprotectsdeepertissues
andorgansintheoralregionfromtheenvironmentof
theoralcavitysoitactas:-
Ashieldprotectingtheunderlyingstructurefrom
chemical,thermaleffects,mechanicalforces
(compression,stretching,andshearing)andsurface
abrasions(fromhardparticlesinthediet).
ABiologicalbarrieragainstmicroorganismsand
theirtoxins.

9. 2-Sensation
Thesensoryfunctionoftheoralmucosais
importantbecauseitprovidesconsiderable
informationabouteventswithintheoralcavity.
Inthemouth,oralmucosacontainreceptors
respondtotemperature,touch,andpain.
Thetongueuniquelyalsohastastebuds.
Reflexessuchasswallowing,gaggingand
salivatingalsoareinitiatedbyreceptorsinthe
oralmucosa.

10. 3-secretion
Themajorsecretionassociatedwiththeoral
mucosaissaliva,producedbythemajorand
minorsalivaryglands.
Salivacontributestothemaintenanceofa
moistandlubricantsurfaceoforalmucosa.

11. 4-Thermal regulation
Insomeanimals(suchasthedogsandcats),
considerablebodyheatisdissipatedthroughtheoral
mucosabypantingsoevaporationofwaterfromthe
surfacemucosacontroltheanimaltemperature.

12. 5-Permeability and Absorption
Mucosaofthefloorofthemouthisverythinso
itallowsrapidabsorptionofdrugs(sublingual
nitrates).

13. III-Boundaries of the Oral Mucosa
Theoralcavityconsistsoftwoareas:
1.Anoutervestibule(boundedbythelipsandcheeks).
2.Oralcavityproper(separatedfromthevestibulebythe
alveolusbearingtheteethandgingiva).
Thehardandsoftpalatesformthesuperiorzoneoftheoral
cavityproper,andthefloorofthemouthandbaseofthe
tongueformtheinferiorborder.
Posteriorlytheoralcavityisboundedbythepillarsofthe
faucesandthetonsils.

15. IV-Classification
Threemaintypesofmucosa:
1.Masticatorymucosa.(amountingto25%ofthetotalarea)
e.g.gingivaandhardpalate.
2.Liningmucosa.(amountingto60%ofthetotalarea)
a)Firmly attached e.g. ventral surface of the tong., inside the
lips, cheeks, and soft palate.
b) Loosely attached. e.g. floor of the mouth, vestibular fornix,
and alveolar mucosa,
3.Specializedmucosa(amounting15%ofthetotalarea).e.g.
dorsumofthetongueandtastebuds.

17. V-Histologicalstructure
Histologicallythehumanoralmucosaconsistsoftwomajor
component:-
(1)Oralepithelium.
(2)Laminapropria(connectivetissue).
Bothofthesetwolayersareseparatedbywelldefined
basementmembrane.
Alsothesetwolayersareattachedeitherdirectlytothe
underlyingstructuresorthroughsubmucosallayer.

20. Oral Epithelium
Theoralepitheliumisectodermalinorigin.
Itisastratifiedsquamousepitheliumconsistingof
cellstightlyattachedtoeachotherandarrangedina
numberofdistinctlayersorstrata.
Likeotherepithelia,theoralepitheliummaintainsits
structuralintegritybyaprocessofcontinuousrenewal
inwhichcellsproducedbymitoticdivisionsinthe
deepestlayers.
Theymatureandundergoterminaldifferentiationas
theymigratepassivelytowardthesurfacetoreplace
thosethatareshed.

21. Thecellsoftheepitheliumthuscanbeconsideredtoconsistof
twofunctionalpopulations:
(A) a progenitor population (the function of which is to divide
and provide new cells)
(B) a maturing population (which continually differentiate or
mature to form a protective surface layer).
Ingeneral,maturationfollowstwomainpatterns:
1. Keratinization .
2. Nonkeratinization

23. Allcellsofbothkeratinizedornon-
keratinizedepitheliumarecalledkeratinocytesas
thesecellscanformkeratinatanytime.
Character of keratinocytes
1-present in sheets.
2-stained with H&E.
3-Have tonofilaments.
4-attached by desmosomes
5-a vascular

24. I-keratinized epithelium
Thistypeisfoundintheareasoforalmucosawhich
subjectedtothemechanicalirritatingeffectoffoodduring
masticationasmasticatorymucosa(hardpalateand
gingiva)andsomeregionofspecializedmucosa(dorsum
ofthetongue).
Epitheliumisinflexibleandtightlyboundtolamina
propria.
Theinterfacebetweenepith.andunderlyinglamina
propriashowsnumerouselongatedpapillae.

25. Keratinized epithelium has 4 layers:
1. The basal layer (stratum basale).
2. The prickle cell layer (stratum spinosum).
3. The granular layer (stratum granulosum).
4. The keratinized layer (stratum corneum).

27. 1-Basal cell layer
Itissinglelayerofcolumnarcellswhich
arrangedinonerowonwelldefinedbasement
membrane.
Cellsofbasallayeraretheleastdifferentiated
cellsoftheepithelium.
Theycontaintheusualcellorganellesin
additioncharacteristicTonofilamentswhich
areformedbyfreeribosomes.
Tonofilamentsgatheredintobundlestoform
tonofibrils.

28. Thecellsarecloselyattachedtoeachotherbyoneormore
typeofcellularjunction(tight,gapanddesmosomal
junction)andalsotothebasementmembraneby
hemidesmosomes.
Thebasalcellsandthefollowing2-3rowsofthespinous
layercellsundernormalcircumstancesundergomitotic
divisionproducingnewcellsthatmatchthoselostatthe
surfacebydesquamation.
oneofthedaughtercellsremainsasprogenitorcelland
theotherwillmigrateupwardandbecomespinous
,granularcellsandfinallychangedtokeratin.

29. Duringtheirmigration,thecellsbecomemorespecialized
andundergobiochemicalandmorphologicalchanges.
N.B
Thebasalcellsaretheprogenitorcellsofthinepithelia
(floorofthemouth)
whilethethickepithelia(egcheekandpalate)the
progenitorcellsaresituatedinthelower2-3layers(basal
andparabasal)andtheyarecalledstratum
germanativum.

31. 2-Spinouscelllayer
Consistofseveralrowsofpolyhedralcellsofdifferent
shapeandsizeandlargerthanthebasalcells.
Thebasalcellsandthespinouscellsformmorethanthe
thicknessoftheepithelium.
Thecellsofthespinouslayerarejoinedtogetherby
intercellularbridges(Desmosomes),Soduringhistologic
preparationthecellsshrinkexceptattheareaswherethey
areheldtogetherbydesmosomes.Thisgivesthemthe
pricklyappearance.

33. Theintercellularspacesarewidecomparedwiththatin
thenon-keratinizedepithelium.
Thespinouscellsarethemostactivecellsinprotein
synthesis.
Thestratumbasalandfirst2-3layersofstratumspinosum
arecalledstratumgerminativumastheygiverisetonew
epithelialcells

34. Thecellshaveawell-developedGolgiapparatus,rough
endoplasmicreticulumandnumerousmitochondria.
Thereisaprogressivedecreaseinsyntheticactivity
throughthelayer.
Thetonofilamentsnetworkanddesmosomesappearto
makeupatensilesupportingsystemfortheepithelial
cells.
Intheupperpartofthestratumspinosumsmall,
intracellularmembrane-coatinggranules(Odlandbodies)
appear.

35. Odland`sbodies (keratinosome) :-
Theypresentinthesuperficiallayerofthespinouscell
layerorinthegranularcelllayer.
Theyhaveaninternallamellatedstructure.
TheymayoriginatedfromGolgisystem
Theyareresponsibleforthethickeningofthecell
membranewhichoccursduringkeratinizationdueto
dischargingofitslipidcontent.
Theymayformanintercellularagglutinatingmaterial.
Theyrichinacidphosphatase

37. 3-granular cell layer
Liesabovethepricklecelllayerandismadeupof
severalrowsofflattenedepithelialcells.
Manyorganellesarereducedorlostsuchthat
cytoplasmispredominantlyoccupiedbythe
tonofilamentsandtonofibrils.
Thecellscontainlargenumbersofsmallbasophillic
granulescalledkeratohyalinegranules.

38. Keratohylinegranules
ByE.M,thegranulesappearSmallandirrigular.
Formedbyribosomes.
Formmatrixproteinflaggrininwhichthetonofillaments
ofthekeratinlayerareembeded.
Causeaggrigationoftonofillaments
Formdisulfidebondbetweenthetonofilaments

39. Odlandbodiesdischargeintotheextracellular
spaces.
Thisisassociatedwiththedevelopmentofabarrier
intheepitheliumthatlimitsthemovementof
substancesbetweenthecells.

40. 4-cornifiedlayer
Itisthefinalstageofmaturationofthekeratinizedepithelium.
Itiscopmosedofkeratinizedsquamaewhicharelargerand
flatterthanthegranularcells.
Thesecellscharacterizedbylossofallorganelles.
Thecellsofstratumcorniumbecomefilledentirelywith
closelybackedtonofilamentssurroundedbythematrixprotein
filaggrin.(keratin).

41. Desmosomesweakenanddisappeartoallowfor
desquamation.
Thelostsquamaearereplacedbycellsfromthe
underlyinglayers.
Thecornifiedlayerproviedsthemechanicalandchemical
protectivefunctionofthemucosa.

42. Types of keratinization:-
A-Ortho-keratinization.
B-Para_keratinization.

43. A-Ortho-keratinization
Asthecellsofgranularlayerreachthejunctionwith
keratinizedlayer,asuddenchangesoccur
Thesechangesare:
1.Alltheorganelleswiththenucleiandkeratohyaline
granulesdisappear.
2.Thecellsdehydrated.
3.Thekeratinizedlayerbecomepackedwithfilaments,
flattened,assumetheformofhexagonaldisks(squames).

44. B-para-keratinization
For masticatory mucosa, parakeratinizationmay occur
dueto:-:
1.Incompleteremovaloforganellesfromthecellsof
granularlayer.
2.Thenucleiremainshrunkenorpyknotic.
3.Remnantsofotherorganellesmaypresentinthe
squames.

45. II-Non keratinized epithelium
Intheregionsoftheoralmucosathatarecoveredbythis
typeofepitheliumshowabsenceofbothkeratinand
granularcelllayer.
Nonkeratinizedepitheliumisthickerandhassmooth
interfacewithC.T.
Thelayersinnonkeratinizedepitheliumare:
1.Basallayer(stratumbasale).
2.Intermediatelayer(stratumintermedium).
3.Superficiallayer(stratumsuperficial).

46. The superficial half of the epithelium divided into two
zones (stratum intermediumand stratum superficial), and
shows changes which distinguishes them from the basal
and prickle cells.
These cells show increase in size , accumulation of
glycogen and occasionally the presence of keratohyaline
granules surrounded by ribosomes. Which appear more
regular and not associated with tonofilaments.

47. Functionofkeratohyalinegranulesappeartobe
associatedwiththickeningofthecellmembrane.
Thecellsofbothstrataarelargerandtightlybacked
together.Theintercellularspacesarenearlyabsentand
hence,absenceofthepricklyappearance.
ThestratumintermediumcontainOdlandbodieswith
theirsize,shapeandlocationaredifferentfromthose
foundinkeratinizedepitheelium

49. Comparison between
keratinized &
non keratinized
epithelium

53. Desmosomes(macula adherans)
•DEF:
localizedspot-likestructuresspecializedforcell-to
celladhesion.theyaretypeofjunctionalcomplexes.
•SITE:
Randomlyarrangedonthelateralsidesofplasma
membranes.
•FUNCTION:
-Formadhesivebonds
-Givesmechanicalstrengthtotissues
frequentlysubjectedtomechanicalforces.

54. •STRUCTURE:
•Thickeningof2adjacentcellmembranes.
•2attachmentplaques.
•Tonofilaments.
•Interveningextracellularstructure.

56. Desmosomes & Hemidesmosomes

57. Nonkeratinocytes
Nonkeratinocytesform10%ofthecellpopulationintheoral
epithelium.
Thesecellsare:-
1.Melanocytes.
2.Langerhan'scells.
3.Markelcells.
4.Inflammatorycells(lymphocytes&PMNL).
Noneofthesecellscontainthelargenumbersoftonofilamentsand
desmosomesseeninepithelialkeratinocytes.
Also,noneofthesecellsparticipateintheprocessofmaturationseen
inoralepithelia;thereforetheyoftenarecalledcollectively
nonkeratinocytes

58. Allthesecells,exceptMerkelcells,lackdesmosomal
attachmenttoadjacentcellssothatduringhistologic
processingthecytoplasmshrinksaroundthenucleusto
producetheclearhalo.
NotstainedwithroutineH&Estain.
Notarrangedinrowsorsheets,butfoundscatteredin
mucosa.
Don’tturnintokeratinocytesorshareinkeratinformation

64. Basementmembrane
Def:
ItisthejunctionbetweentheepitheliumandtheC.T
Function:
1.Diffusionbarrier(controlexchangeofmolecule).
2.Filtrationbarrier(kidney)
3.Orientlocationandmovementofepithcells.
4.Elasticsupportforepithcells.
Shape:
Itmaybeirregularwithlongslenderretepigsorshortbluntprocesses

65. Basement membrane under the microscope:
ByL.M:(basementmembrane)
Structurelessbandin(H&E)
1-4m,appearsasundulatinglineasaresultofepithelial
retepegsinterdegitatewithC.Tpapilla
Stainedwith:PAS(proteoglycans)brightstructure
less

66. By EM: it is termed Basal lamina.
(lamina lucidaand lamina densa+ anchoring fibers)
1-laminalucida(clearzone):
Liesimmediatlyundertheepithelim
Epithelialinorigin
Is20-40nmthick.
Consistofglycoproteincalledlamininthatcementsnon-
fibrillartypeIVcollagenwhichpresentinlaminadensatothe
epithelialcells.

67. 2-laminadensa(darkzone):
Liesdeeptolaminalucida
Epithelialinorigin
Is20-120nmthick(thickerthanlaminalucida)
ConsistofcollagenIV+heparinsulfate+laminin.

68. 3-Anchoring fibers (lamina fibro articularis)
OriginatesfromfibroblastsoftheC.T.
ConsistofcollagenVII.
Itisasystemoffinefilamentsthatpenetratethe
laminadensafromtheC.Tsideandreachesthe
plasmamembraneofthebasalcells,mostlyinthe
regionofhemidesmosomes.
Thesefinfilamentsformbundleswhichinterdigitate
withthecollagenfibersofthelaminapropria.

70. Epithelialretepigs:
Theyarethedownwardprojectionsofepitheliuminthe
underlyingCT.
Theseridgesinterdigitatewithupwardprojecting
connectivetissuepapillae.
Inmasticatorymucosa:hasgreatestNO.oftheepithelial
ridgesperunitarea(long-slender)foradaptationto
functionandappliedforce.
Inliningmucosa:theyarelessnumerous,broaderand
shorter.

71. Functionofepithretepigs:
Increasesurfacearea
Providebetterattachment.
Betterdistributionofforce
Largeinterfaceformetabolicexchange(noB.Vinepi)

72. Lamina propria
Itiscomposedofdenseconnectivetissueofvariable
thicknesswhichplaysaroleinsupportingandsecuring
thenutritionalandmetabolicexchangeintothe
epithelium.
Itmayattachtheperiosteumoroverlaythesubmucosa.
Morphologically,thelaminapropriamaybedividedinto
twoareas
1.papillarylayer
2.reticularlayer.

73. Laminapropriaisformedof:
Cells
1.Syntheticcells(fibroblasts,fatcells,andUMC).
2.Defensivecells(lymphocytes,plasmacells,macrophages,
monocytes,mastcells,andneutrophils).
Bloodvessels
Lymphaticdrainage
Nervesupply
Fibers
Allthesecomponentsareembeddedinamorphousgel-like
groundsubstanceformedofglycoproteinsandproteoglycans.

74. 1-Papillarylayer:-
ItisformedoflooseC.T
Adjacenttotheepitheliumandsurroundingthe
epithelialridges
Thislayermaybeabsentifretepigs are
absentortooshort.

75. 2-Thereticularlayer:
Networkofdensecollagenfibers.
Theyarearrangedhorizontallyinthedirectionof
minimumextensibilitytopreventmucosal
deformation.
Fewelasticfibersarefoundtorestoredeformed
collagen.
Alwayspresent