20-Plcenta.ppt.ppt

Fetalmembraneandplacenta,Decidua:Aftertheimplantationoftheembryo,theuterineendometriumiscalledthedecidua.Thestramalcellsenlrge,becomevacuolatedandlipids.Thischangeinthestromalcellsiscalledthedeciduareaction.,Thedeciduaisdividedintothreepartsaccordingtotheassociationwiththeembryo:Deciduabasalis:deeptotheembryoDeciduacapsulris:overtheembryoDeciduaparitalis:theleftpartofdecidua,Deciduabasalis,Deciduaparitalis,Deciduacapsulris,ChorionAmnionYolksacallantoisUnbiliadcord,Fetalmembrane:,Lacuna,cytotrophoblast,syncytiotrophoblast,Extraembryonicmesoderm,Chorion:Formationofchorion:Thecytotrophoblastdifferentiatesinternallyintoalayerofprimarymesoderm.Trophoblastandprimarymesodermtogetherformthechorion.Theygiveoffnumerousprocesscalledvilliorchorionicvilli.Thesevilliaresurroundedbymaternalblood.,Thechorionicvilliarefirstformedalloverthetrophoblastandgrowintothesurroundingdecidua.thoserelatedtothedeciduacapsularisaretransitory.Aftersometimetheydegenerate.Thispartofthechorionbecomessmoothandiscalledthechorionlaevae.,Incontrast,deciduaundergoconsiderabledevelopment.Alongwiththetissuesofthedeciduabasalisthesevilliformadisc-shapedmasswhichiscalledtheplacenta.Thepartofthechorionthathelpsformtheplacentaiscalledthechorionfrondosum.,Germdisc,Amnion,Yolksac,chorion,Connectingstilk,Amnion,Connectingstilk,Extraembryoniccavity,Yolksac,Extraembryoniccavity,Yolksac,Umbilicalcord,Amnioticcavity,Amnioticcavity,Umbilicalcord,amnion,Chorionlaevae,Allelements(syncytium,cytotrophoblastandmesoderm)takepartinformingchorionicvilli.Threestagesinformationofchorionicvilliareseen:Aprimaryvillus:cytotrophoblastandiscoveredbythecellsofsyncytiotrophoblast.,Asecondaryvillus:primarymesodermandiscoveredsuccessivelybycyto-andsyncytiotrophoblasts.Atertiaryvilluscontainsinthecenterthefoetalbloodvesselswhicharesurroundedsuccessivelyfromwithinoutwardsbyprimarymesoderm,cytoandsyncytiotrophoblasts.,capillary,Intervillispace,decidua,Syncytiotrophoblast,cytotiotrophoblast,capillary,Connectivetissue,Cellshell,Fromeachtertiarystemvillusnumerousbranchingvilliprojectintotheintervillousspace.theintervillousspaceisconvertedintoasponge-likenetworkofvilloustypeoflabyrinthinestructureandisfilledwithmaternalblood.,THEAMNIOTICCAVITYAfluid-filledamnioticcavityappearsinthesecondweekofdevelopmentbetweenthegermdiscandthetrophoblast.Theroofofthecavity:alayerofflattenedcells,theamnioblast,whichlinestheinneraspectofthecytotrophoblast.Thefloorofthecavity:thetallcolumnarcellsoftheepiblastofthegermdisc.,Epiblast,Hypioblast,Aminioticcavity,Connectingstalk,二胚层的羊膜,三胚层的胎膜,Withtheextensionoftheextra-embryoniccoelomtheoutersurfacesoftheamnioticcavityandtheyolksacarecoveredwithalayerofprimarymesoderm,whichiscontinuouswiththeprimarymesodermofthechorionatthecaudalendofthegermdiscthroughtheconnectingstalk.,Theformationoftheembryonicfoldsallowstheamnioticcavitytosurroundtheoutersurfaceofthecylindricalembryo.Asaresulttheamnio-ectodermaljunctionconvergestowardstheventralsurfaceoftheembryotoformtheumbilicalcord,Theamnioticcavitygraduallyincreasesinsizeattheexpenseoftheextra-embryoniccoelom,andeventuallytheamnionandchorionleavearefused.Finallytheextra-embryoniccoelomiscompletelyobliterated,exceptasmallpartwhichiscontainedintheproximalpartoftheumbilicalcorduptothe10thweekofintra-uterinelife.,Germdisc,Amnion,Yolksac,chorion,Connectingstilk,Amnion,Connectingstalk,Extraembryoniccavity,Yolksac,Extraembryoniccavity,Yolksac,Umbilicalcord,Amnioticcavity,Amnioticcavity,Umbilicalcord,amnion,Chorionlaevae,TheAmnioticFluidTheamnioticfluid,alsocalledliquoramnii,isclearandwatery,containingabout2%solidswhichincludeinorganicsalts,urea,proteinsandatraceofsugar.Thesourceofthefluidstillremainsunsettled-itmaybefoetalfromtheamnioticcells,maternalorboth.,Functionsoftheliquoramnii-1.Itactsasaprotectivecushionfortheembryoagainstshock,blowsorpressure.Theembryoissuspendedbytheumbilicalcordandliterallyswimsinthefluid.2.Thefluidmaintainsauniformpressureforthepropergrowthanddifferentiationofthedelicatetissuesoftheembryo.,3.Itallowsfoetalmovementsandmaintainsaconstantenvironmentaltemperature.4.Duringparturition,theamnioticsacformsahydrostaticwedgeandhelpstodilatethecervicalcanal.,Abnormalitiesoftheliquoramnii-1.HydramniosThisisaconditionwhenthevolumeoftheamnioticfluidexceedstwolitres.2.Oligamnios-Inthisconditionthefluidisscantyinamount.,YolksacPrimaryYolksacsecondaryyolksac,Epiblast,Hypioblast,Aminioticcavity,allantois,Primitivefemalesexcell,Yolksac,.Vitello-intestinalductItcommunicatesthemidgutwithextra-embryonicpartoftheyolksac(umbilicalvesicle).Inthelaterpartoffoetallifetheductdisappears.Onrareoccasions,theproximalpartoftheductpersistsastheMeckelsdiverticulumwhichisattachedtotheantimesentericborderoftheileum.,allantois,Allanto-entericdiverticulumorallantois:Associatedwiththeformationofthecloacalmembrane,atubularendodermaloutgrowthknownasallanto-entericdiverticulumorallantoisarisesfromthedorsi-caudalendoftheyolksacextendsintotheprimarymesodermoftheconnectingstalk.,Probablyinmantheallantoishelpstovascularisethechorionanditsvilliwiththeallantoicorumbilicalbloodvessels.,Thedistalpartofthediverticulumisfibrosedtoformtheurachusandtheproximalpartincorporateswiththeapexoftheurinarybladder.Ifthelumenofthediverticulumpersistsentirelyafterthefallingoffofthecord,aurinaryfistulatakesplaceattheumbilicus.,Placenta,Humanplacentaisadiscoid,chorio-deciduateorganwhichconnectsthefoetuswiththeuterinewallofthemother.Itisastructurewherematernalandfoetaltissuescomeindirectcontactwithoutrejection,suggestingimmunologicalacceptanceofthefoetalgraftbythemother.,GrossAnatomy-Atfulltermtheplacentaisdisclike,andpresentsafterseparationfromtheuterinewallfoetalandmaternalsurfaces,andperipheralmargi,Foetalsurfaceissmooth,coveredbyamnionandpresentstheattachmentoftheumbilicalcordclosetoitscenter.Beneaththeamnionumbilicalvesselsradiatefromthecord.,Maternalsurfaceisroughandirregular,andismappedoutinto15-30polygonalareasknownasthecotyledonswhicharelimitedbyfissures.Eachfissureisoccupiedbyaplacentalseptum.,Peripheralmarginiscontinuouswiththefoetalmembranewhichconsistsfromoutsideinwardsoffuseddeciduasparietalisandcapsularis,chorionlaeveandamnion.MeasurementsAtfulltermtheplacentapresentsthefollowingmeasurements:Diameter-15to20cm.Thickness-3cm.(atthecenter).Weight-500gms.,Structureoftheplacenta,Bythebeginningofthefourthmonth,theplacentahastwocomponents:(a)afetalportion,formedbythechorionfrondosum(b)amaternalportion,formedbythedeciduabasalis,Placentaisdevelopedfromtwosources-foetalpartfromchorionfrondosumandmaternalpartfromdeciduasbasalis.Theplacentaconsistsofchorionicplateonthefoetalside,basalplateonthematernalside,stemvilliextendingbetweentheplates,andintervillousspacebetweenthestemvillifilledwiththematernalblood.,Onthefetalside,theplacentaisborderedbythechorionplate;Onthefetalside,theplacentaisborderedbythedeciduabasalisofwhichthedecidualplateismostintimatelyincorporatedintotheplacenta.,Chorionicplate:(1)Villi:Fixedstemvilli:cytotrophoblastemergesthroughthesyncytiumofeachvillus,andattachedtothedeciduaFreestemvilli:cannotcontactwiththedecidua,justfloatinthebloodoftheintervillusspace.(2)Intervilloussapce:surroundingthevillifilledinthematernalblood.,Thebasalplateisperforatedbythespiralbranchesofuterinearteriesandveins;eventuallytheintervillousspaceisfilledwithmaternalblood.Theportionsofthebasalplateinbetweenthestemvilliprojectintotheintervillousspaceasplacentalsepta.Numerousplacentalseptaprojectfromthebasalplateintotheintervillousspacebuttheyfailtoreachthechorionicplate.,Placentalcirculation:Maternalbloodintheintervillousspace-FoetalBloodinthevilliofthePlacenta,Theplacentalbarrierconsistsoftissueswhichintervenebetweenfoetalbloodinthechorionicvilliandmaternalbloodintheinterv