5 connective tissue pics legends.docx
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5 connective tissue pics legends.docx
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5connectivetissuepicslegends
Figure5–1.
Embryonicmesenchyme.Mesenchymeconsistsofapopulationofundifferentiatedcells,generallyelongatedbutwithmanyshapes,havinglargeeuchromaticnucleiandprominentnucleoliwhichindicatehighlevelsofsyntheticactivity.Thesecellsarecalledmesenchymalcells.Mesenchymalcellsaresurroundedbyanextracellularmatrixwhichtheyproducedandwhichconsistslargelyofasimplegroundsubstancerichinhyaluronan(hyaluronicacid).ThissectionisstainedwithMassontrichromewhichstainscollagenfibersblueandthelackofcollageninmesenchymeisapparent.X200.
Figure5–2.
Lineagesofconnectivetissuecells.Thissimplifiedrepresentationoftheconnectivetissuecelllineageincludescellsfromthemultipotentialembryonicmesenchymecellsandhematopoieticstemcellsofbonemarrow.Dottedarrowsindicatethatoneormoreintermediatecelltypesexistbetweentheexamplesillustrated.Thecellsarenotdrawninproportiontoactualsizes,eg,adipocyte,megakaryocyte,andosteoclastcellsaresignificantlylargerthantheothercellsillustrated.
Figure5–3.
Fibroblasts.Connectivetissuewhereparallelbundlesofcollagenarebeingformed.(a):
Fibroblaststypicallyshowlargeactivenucleiandeosinophiliccytoplasmtaperingoffinbothdirectionsalongtheaxisofthenucleus,amorphologyusuallycalled“spindle—shaped.”Thenuclei(arrows)areclearlyseen,butthecytoplasmicprocessesresemblethecollagenbundles(C)thatfilltheextracellularmatrixandaredifficulttodistinguishinH&E—stainedsections.(b):
Bothactiveandquiescentfibroblastsmaysometimesbedistinguished,asinthissectionofdermis.Activefibroblastsarelargecellswithlarge,euchromaticnucleiandbasophiliccytoplasm,whereasinactivefibroblastorfibrocytesaresmallerwithlessprominent,heterochromaticnuclei.Theverybasophilicroundcellsin(b)areleukocytes.BothX400.H&E.
Figure5–3.
Fibroblasts.Connectivetissuewhereparallelbundlesofcollagenarebeingformed.(a):
Fibroblaststypicallyshowlargeactivenucleiandeosinophiliccytoplasmtaperingoffinbothdirectionsalongtheaxisofthenucleus,amorphologyusuallycalled“spindle—shaped.”Thenuclei(arrows)areclearlyseen,butthecytoplasmicprocessesresemblethecollagenbundles(C)thatfilltheextracellularmatrixandaredifficulttodistinguishinH&E—stainedsections.(b):
Bothactiveandquiescentfibroblastsmaysometimesbedistinguished,asinthissectionofdermis.Activefibroblastsarelargecellswithlarge,euchromaticnucleiandbasophiliccytoplasm,whereasinactivefibroblastorfibrocytesaresmallerwithlessprominent,heterochromaticnuclei.Theverybasophilicroundcellsin(b)areleukocytes.BothX400.H&E.
Figure5–4.
Macrophageultrastructure.CharacteristicfeaturesofmacrophagesseeninthisTEMofonesuchcellaretheprominentnucleus(N)andthenucleolus(Nu)andthenumeroussecondarylysosomes(L).Thearrowsindicatephagocyticvacuolesneartheprotrusionsandindentationsofthecellsurface.X10,000.
Figure5–5.
Mastcells.Mastcellsarecomponentsoflooseconnectivetissues,oftenlocatednearsmallbloodvessels(BV).(a):
Theyaretypicallyoval—shaped,withcytoplasmfilledwithstronglybasophilicgranules.X400.PT.(b):
Ultrastructurallymastcellsshowlittleelsearoundthenucleus(N)besidesthesecytoplasmicgranules(G),exceptforoccasionalmitochondria(M).ThegranulestainingintheTEMisheterogeneousandvariableinmastcellsfromdifferenttissues;athighermagnificationssomegranulesmayshowacharacteristicscroll—likesubstructure(inset)thatcontainspreformedmediatorssuchashistamineandproteoglycans.TheECMnearthismastcellincludeselasticfibers(E)andbundlesofcollagenfibers(C).
Figure5–6.
Mastcellsecretion.Mastcellsecretionistriggeredbyre—exposuretocertainantigensandallergens.MoleculesofIgEantibodyproducedinaninitialresponsetoanallergensuchaspollenorbeevenomareboundtosurfacereceptorsforIgE
(1),ofwhich300,000arepresentpermastcell.Whenasecondexposuretotheallergenoccurs,IgEmoleculesbindthisantigenandafewIgEreceptorsveryrapidlybecomecross—linked
(2).Thisactivatesadenylatecyclase,leadingtophosphorylationofspecificproteinsand(3)entryofCa2+andrapidexocytosisofsomegranules(4).Inaddition,phospholipasesactonspecificmembranephospholipids,leadingtoproductionandreleaseofleukotrienes(5).Thecomponentsreleasedfromgranules,aswellastheleukotrienes,areimmediatelyactiveinthelocalmicroenvironmentandpromoteavarietyofcontrolledlocalreactionswhichtogethernormallycomprisepartoftheinflammatoryprocesscalledtheimmediatehypersensitivityreaction.ECF—A,eosinophilchemotacticfactorofanaphylaxis.
Figure5–7.
Plasmacells.Plasmacellsareabundantinthisportionofaninflamedintestinalvillus.Theplasmacellsarecharacterizedbytheirabundantbasophiliccytoplasminvolvedinthesynthesisofantibodies.AlargepaleGolgiapparatus(arrows)neareachnucleusisthesiteoftheterminalglycosylationoftheantibodies(glycoproteins).Plasmacellscanleavetheirsitesoforigininlymphoidtissues,movetoconnectivetissue,andproducetheantibodiesthatmediateimmunity.X400PT.
Figure5–8.
TypeIcollagen.MoleculesoftypeIcollagen,themostabundanttype,assembletoformmuchlargerstructures.(a):
TEMshowsfibrilscutlongitudinallyandtransversely.Inlongitudinalsectionsthefibrilsdisplayalternatingdarkandlightbandsthatarefurtherdividedbycross—striationsandincross—sectionthecutendsofindividualcollagenmoleculescanbeseen.Groundsubstancecompletelysurroundsthefibrils.X100,000.(b):
InH&Estainedtissues,typeIcollagenfibrilscanoftenbeseentoaggregatefurtherintolargecollagenbundles(C)ofveryeosinophilicfibers.Subunitsforthesefibersweresecretedbyfibroblasts(arrows)associatedwiththem.X400.
Figure5–8.
TypeIcollagen.MoleculesoftypeIcollagen,themostabundanttype,assembletoformmuchlargerstructures.(a):
TEMshowsfibrilscutlongitudinallyandtransversely.Inlongitudinalsectionsthefibrilsdisplayalternatingdarkandlightbandsthatarefurtherdividedbycross—striationsandincross—sectionthecutendsofindividualcollagenmoleculescanbeseen.Groundsubstancecompletelysurroundsthefibrils.X100,000.(b):
InH&Estainedtissues,typeIcollagenfibrilscanoftenbeseentoaggregatefurtherintolargecollagenbundles(C)ofveryeosinophilicfibers.Subunitsforthesefibersweresecretedbyfibroblasts(arrows)associatedwiththem.X400.
Figure5–9.
Procollagen.Inthemostabundantformofcollagen,typeI,eachprocollagenmoleculeiscomposedoftwoα1andoneα2peptidechains,eachwithamolecularmassofapproximately100kDa,intertwinedinaright—handedhelixandheldtogetherbyhydrogenbondsandhydrophobicinteractions.Eachcompleteturnofthehelixspansadistanceof8.6nm.Thelengthofeachtropocollagenmoleculeis300nm,anditswidthis1.5nm.
Figure5–10.
Assemblyofcollagenmoleculesintocollagenfibers.Thisdiagramshowsanaggregateofcollagenmolecules,fibrils,fibers,andbundles.Thereisastepwiseoverlappingarrangementofrodlikecollagenmolecules,eachmeasuring300nm
(1).Thisarrangementresultsintheproductionofalternatingspacesandoverlappingregions
(2),whichcausethecross—striationscharacteristicofcollagenfibrilsandconfera67—nmperiodicityofdarkandlightbandswhenthefibrilisobservedintheelectronmicroscope(3).Fibrilsaggregateandarecovalentlycross—linkedtoformfibers(4),whichincollagentypeIaggregatefurthertoformbundles(5)routinelycalledcollagenfiberswhenseenbylightmicroscopy.
Figure5–11.
Collagensynthesis.HydroxylationandglycosylationofprocollagenαchainsandtheirassemblyintotriplehelicesoccursintheRERandfurtherassemblyintofibrilsoccursintheECMaftersecretionofprocollagen.Becausetherearemanyslightlydifferentgenesforprocollagenαchainsandcollagenproductiondependsonseveralpost—translationaleventsinvolvingseveralotherenzymes,manydiseasesinvolvingdefectivecollagensynthesishavebeendescribed.
Figure5–12.
Reticularfibers.Inthesesilver—stainedsectionsofbothadrenalcortex(a)andlymphnode(b),theprominentfeatureisanetworkofreticularfiberswhichprovidesaframeworkforcellattachment.ReticularfiberscontaintypeIIIcollagenthatisheavilyglycosylated,whichproducestheargyrophilia.Cellnucleiarealsodarkbutcytoplasmisunstained.X100.
Figure5–13.
Elasticfibers.Elasticfibersorlamellae(sheets)addtheresiliencytoconnectivetissue.TheyaredifficulttodiscerninH&Estainedmaterialandareusuallydemonstratedinpreparationsmadeusingcompoundssuchasaldehydefuscinwhichstainselastinadarkmagenta.(a):
Thelengthanddensityoffineelasticfibersisbestseeninspreadpreparationofconnectivetissueinathinmesentery.X200.Orcein—H&E.(b):
Athighermagnification,sectionedelasticfiberscanbeseenamongtheeosinophiliccollagenbundlesindermis.X400.Aldehydefuscin&eosin.(c):
Elasticfibersandlamellaeareabundantbetweenlayersofsmoothmuscleinthewallofelasticarteriessuchastheaorta.X200.VanGieson—H&E.
Figure5–14.
Formationofelasticfibers.StagesintheformationofelasticfiberscanbeseenbyTEM.(a):
Initiallyadevelopingfiberconsistsofmanysmallmicrofibrilscomposedoftheglycoproteinfibrillinsecretedbyfibroblasts,smoothmusclecellsorothercells.(b):
Withfurtherdevelopment,tothemicrofibrilsareaddedamorphousdeposi
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