Epithelium - General Histology DDS6214 · PDF fileEpithelium Lecture Outline • Func.on...
Transcript of Epithelium - General Histology DDS6214 · PDF fileEpithelium Lecture Outline • Func.on...
EpitheliumLectureObjec.ves
• Describethestructuralandfunc.onalrela.onshipbetween:• epitheliumandconnec.ve.ssue,and• epitheliumandbasallamina.
• Describethestructuralandfunc.onalfeaturesofepithelialintercellularjunc.onsandspecializa.onsoftheapicalsurfaceofepithelialcells.
MoreEpitheliumLectureObjec.ves
• Describethestructuralandfunc.onaldiversityofepithelium.
• Describetheclassifica.onsystemofcovering/liningepithelium.
• Describethehistologicfeaturesofglandularepithelium.
EpitheliumLectureOutline
• Func.onandtypesofepithelium
• Structureofepithelium
• Typesofcovering/liningepithelium
• Typesofglandularepithelium
Func.onsofEpithelium
• Coveringofexternalsurfaces• Liningofinternalsurfaces• Protec.on• Absorp.on• Secre.on• Sensa.on• Contrac.on
TwoMainKindsofEpithelium
CoveringandliningepitheliumCoversoutersurfacesofbodyandlinesinternalbodypassages
GlandularepitheliumContainscellsspecializedforsecre.on
UniqueCharacteris.csofEpithelium
• Basallaminaanchorsepitheliumtounderlyingconnec.ve.ssue.
• Epithelialcellsareverycohesiveduetointercellularjunc.ons.
• Epithelialcellsvaryalotinshapeandsize.
• Epithelial.ssuesareavascular.
• Epithelialcellsdemonstratepolarity.
EpitheliumLectureOutline
• Func.onandtypesofepithelium
• Structureofepithelium• Basementmembrane• Connec.onsbetweencells• Specializedapicalstructures
Basallamina
Re.cularlamina
Anchoringfibrils(typeVIIcollagen)
Anchoringplaques(typeIVcollagen)
Re.cularfibers(typeIIIcollagen)
Epithelialcell
TypeIVcollagenandperlecan
(aproteoglycan)
Laminin(aglycoprotein)
laminalucida
laminadensa
Composi.onofBasalLaminaandRe.cularLamina
Func.onsofBasalLamina
• Structure:aXachesepitheliumtoconnec.ve.ssue
• Organiza.on:arrangesplasmamembraneproteinsinthebasalmembrane
• Filtra.on:regulatesmovementofmaterialbetweenepitheliumandconnec.ve.ssue
Don’tmakethismistake!
“Basallamina”and“basementmembrane”aresome.mesusedinterchangeably.
Thisiswrong,wrong,wrong!
Thebasallaminaispartofthebasementmembrane.Theyarenotthesamething.
EpitheliumLectureOutline
• Func.onandtypesofepithelium
• Structureofepithelium• Basementmembrane• Intercellularjunc.ons
Intercellularjunc.onsconnectepithelialcells
Intercellularjunc.onsarepresentinmost.ssuesbutareespeciallynumerousandprominentinepithelium.
• Zonulaoccludens(.ghtjunc.on)
• Zonulaadherens(beltdesmosome)
• Maculaadherens(desmosome)
• Hemidesmosomes
• Gapjunc.on(nexus)
Zonaoccludens(.ghtjunc.on)
• Mostapicaljunc.oninepithelium
• Formbands(zonula)thatcompletelyencircleeachcell
• Membranesofadjacentcellsfusetosealofftheintercellularspace
Zonaoccludens(.ghtjunc.on)
• Claudinsandoccludinsaretwofamiliesofproteinsthatformasealtopreventflowofmaterialsbetweenepithelialcells
• Morezonaoccludens=.ghterseal
Zonulaadherens(beltdesmosome)
• Formbandsthatcompletelyencircleeachcell
• Cadherinandcateninproteinsprovideadhesionbetweenadjacentcells
• Ac.nfilamentsincytoplasminsertintoaXachmentplaques
Maculaadherens(spotdesmosome)
• Spotadhesionbetweencells
• Desmosomesonadjacentcellslineup
• Cadherinspresentinintercellularspace
Maculaadherens(spotdesmosome)
• Cytokera.nintermediatefilamentsinsertintoaXachmentplaquescontainingdesmoplakinandplakoglobin
• SuperstrongaXachmentpointsbetweencells
• Themoredesmosomes,themore.ghtlytheepithelialcellsareaXached
Pemphigusvulgaris
• Ablisteringdiseaseinwhichpa.entsmakeautoan.bodiestodesmogleinproteins
• Epithelialcellconnec.ons(spotdesmosomes)loosen,causingfluidaccumula.onandsuperficialblisters
Cytokera.nintermediatefilaments
CytoplasmicaXachmentplaques
Plasmamembranes
Maculaadherens(spotdesmosome)
HemidesmosomesaXachepithelialcellstobasallamina.IntegrinsaXachthebasalpor.onofthecelltothebasallamina.
Hemidesmosomes
Bullouspemphigoid
• Ablisteringdiseaseinwhichpa.entsmakeautoan.bodiesto“bullouspemphigoidan.gen”inhemidesmosomeaXachmentplaques
• Epithelialcellsdetachfrombasallamina,causingfluidaccumula.onandblisterforma.on
Junc.onalcomplexofintercellularjunc.ons
• ZO:zonulaoccludens• ZA:zonulaadherens• D:desmosome
• Insometypesofepithelia(simplecolumnarofdiges.vetract)junc.onsoccurinthisorder
Gap(communica.ng)junc.on• Occuralmostanywhere
alonglateralsurfacesofepithelialcellsandalsoinothercells,suchascardiacmusclecells
• Connexonsareproteinchannelswithcentralporesconnec.ngplasmamembranes
• Allowionsandothersmallmoleculestopassthroughtoadjacentcellstofacilitatecommunica.on
EpitheliumLectureOutline
• Func.onandtypesofepithelium
• Structureofepithelium• Basementmembrane• Intercellularjunc.ons• Specializedapicalstructures
Microvilli
Microvilli+cellcoat(orglyocalyx)=brushborderorstriatedborder
Purposeofmicrovilli:increasesurfaceareaforabsorp.onorsecre.on
Microvillus
Tight junctions
Belt desmosome
Spot desmosome
Gap junction
Intermediate filament
Hemidesmosome
Basal lamina
Microvilli
Microvillihaveacentralcoreof
ac.nmicrofilaments
Microvillidon’twavebackandforthlikecilia.
Stereocilia
Stereociliaarelong,non-mo.lemicrovilli
foundinpartsofthemalereproduc.vesystem
Stereocilia
Spermatozoa
CiliaCiliaaremuchlongerandwiderthanmicrovilli.
Theymovebackandforthtopropelfluidalongtheepithelialsurface.
Ciliaonrespiratoryepithelialcells
CiliaCiliacontainmicrotubulesina9+2configura.oncalledan“axoneme”
2centralmicrotubulessurroundedby9pairsofmicrotubules
Ciliainsertintobasalbodieswith9tripletsofmicrotubules
EpitheliumLectureOutline
• Func.onandtypesofepithelium
• Structureofepithelium
• Typesofcovering/liningepithelium
Howiscovering/liningepitheliumcategorized?
Shapeofsuperficialcells
Numberofcelllayers
Presenceofspecializedstructures
Howiscovering/liningepitheliumcategorized?
Shapeofsuperficialcells• Squamous:width>height(flaXened)• Cuboidal:width=height(square,round)• Columnar:width<height(tallandslender)
Epithelialcellshavedifferentshapes
squamouscellsareflat cuboidalcellsarecuteandboxy
columnarcellsaretallandregal
Howiscovering/liningepitheliumcategorized?
Shapeofsuperficialcells
Numberofcelllayers• Simple:onelayerofcells• Stra.fied:twoormorelayersofcells• Pseudostra.fied:allcellscontactbasallamina,butnotallcellsreachlumen
Simpleepithelium:onelayerofcells
Simplesquamousepithelium Simplecuboidalepithelium
Simpleciliatedcolumnarepithelium
Endotheliumissimplesquamousepithelium.Itlinesbloodandlympha.cvessels.
SimpleSquamousEpithelium
FlaXenedsquamouscellsinasinglelayer
Mesotheliumissimplesquamousepithelium.Itlinesserouscavi.es(pleura,pericardium,peritoneum).
SimpleSquamousEpithelium
FlaXenedsquamouscellsinasinglelayer
Ductliningso1enhavesimplecuboidalepithelium,likethissmallishductinthepancreas.
SimpleCuboidalEpithelium
Cuboidalcells
inonecutelayer
Stra.fiedSquamousEpithelium
Severallayersofsquamousepithelialcells
Mucousmembranesarecomposedofstra.fiedsquamousepithelium.
Someductsarelinedbystra.fiedcuboidalepithelium,likethislargerductinthepancreas.
Stra.fiedCuboidalEpithelium
Cuboidalcells
inafewlayers
Howiscovering/liningepitheliumcategorized?
Shapeofsuperficialcells
Numberofcelllayers
Presenceofspecializedstructures• Cilia• Microvilli• Kera.n
Pseudostra.fiedCiliatedColumnarEpitheliumgobletcell cilia
Respiratoryepitheliumispseudostra.fiedcolumnar,withgobletcellsandciliatedcells.
SimpleColumnarEpithelium
Theepitheliumofthesmallintes.neissimplecolumnar,withgobletcellsandabsorp.vecellswithmicrovilli.
gobletcellmicrovilli
Kera.ncoversareaswhereskinisthinbutneedsprotec.on.
Kera.nizedStra.fiedSquamousEpithelium
Squamouscells
inseverallayers
Kera.n
Areasthatarealwaysmoist(liketheesophagus)areo1enlinedbystra.fiedsquamousepitheliumwithoutalayerofkera.n.
Non-Kera.nizedStra.fiedSquamousEpithelium
Squamouscells
inseverallayers
Nokera.n!
EpitheliumLectureOutline
• Func.onandtypesofepithelium
• Structureofepithelium
• Typesofcovering/liningepithelium
• Typesofglandularepithelium
• Mucousgobletcell:unicellulargland
• Exocrinegland:retainsconnec.onwithsurfaceepithelium;hormonessecretedthroughducts
• Endocrinegland:noconnec.onwithsurfaceepithelium;hormonessecretedthroughblood
TypesofGlandularEpithelia
• Merocrine:secretorygranulesleavecellbyexocytosis.Mostcommonmethod.
• Holocrine:Secretoryproductshedwithen.recell.Example:sebaceousgland
• Apocrine:secretoryproductshedwithapicalcytoplasm.Example:mammarygland
Methodsofsecre.oninexocrineglands
• Secretesbymerocrinemodeofsecre.on:exocytosisofproductatapicalendofcell.
• Byfarthemostcommontypeofexocrineglandbasedonmodeofsecre.on.
Merocrinegland
Examplesofglandularepithelialcells
• Iontranspor.ngcells
• Seroussecretorycells
• Mucoussecretorycells
• Neuroendocrinecells
• Myoepithelialcells
Ion-transpor.ngcells
• Deepinvagina.onsofbasalcellmembranes
• Zonulaoccludens
• Mitochondriainbasalcytoplasmprovideenergyforiontransport
• Examples:proximaltubulesinkidney
Seroussecretorycells
• LargeroundednucleusandabundantroughER,Golgiandsecretorygranules
• Examples:pancrea.cacinarcells,serouscellsinsalivaryglands
Mucoussecretorycells
• AbundantroughER,Golgiandsecretorygranules
• Producemucins(protec.ve,lubricantglycoproteins)
• Examples:mucouscellsinstomach,gobletcellsinsmallandlargeintes.ne,andmucouscellsinsalivaryglands
Neuroendocrinecells
• Densesecretorygranulesincytoplasmcontainpolypep.desand/oramines(likeepinephrineandnorepinephrine)
• ScaXeredthroughoutthebody
Myoepithelialcells
• Spindle-shapedcellsfoundinglandularepithelialbetweenbasallaminaandbasalcytoplasm
• Embraceglandacinilikean“octopusonarock”
• Containac.n:contractandsqueezeoutsecretoryproduct