Kehitysvaiheet
Selkärangattomat
Selkärangattomatincludemorethan30phyla,about22timesthenumberofspeciesofchordates,almostexistingontheearthInvariousenvironments.Becausedifferentspeciesofanimalshavedifferentdevelopmenthistories,differentformsanddifferentreproductionmethods,theirembryonicdevelopmentshowsahighdegreeofdiversityandcomplexity.Underthiscircumstance,thevariousconnectionsbetweentheembryonicdevelopmentofdifferentclassesofinvertebratesneedtobesummarizedandanalyzedfromdifferentangles.
Asweallknow,theprimarycharacteristicofinvertebrateembryodevelopmentisthatitsprocessisnotlimitedtotheeggmembraneorthemother'sbody,andtherearelarvalstagesinmanyspecies.Fromlarvatoadult,ithastoundergometamorphosis.Measuredbythedegreeofmorphogenesis,theinvertebratelarvalstageisstilltheembryonicstage.Embryologistscalldevelopmentthatdoesnotgothroughthelarvalstageasdirectdevelopment,andthedevelopmentthatgoesthroughthelarvalstageasindirectdevelopment.
Theembryonicdevelopmentofmostinvertebratesiscarriedoutonthebasisofsexualreproduction,andafewspeciesalsodevelopparthenogeneticembryos.MostoftheMustelasintheclassPneumocystisonlyundergothelattertypeofembryonicdevelopmentduetolackofmalereproductiveorgans.Inaddition,sometypesofasexualreproductionandregenerationaresimilartoembryonicdevelopment.
Inadditiontothestagesofinvertebrateembryodevelopmentthatgenerallygothroughcleavage,blastocyst,gastrulation,larvaeandadultorganogenesis,thereisalsoanThetransitionalstageofthepost-larvalstage,suchasthepost-larvalstageofprawns,hasallappendages,buthasnotyetreachedtheadultlevelintermsofbody-to-bodyratio,appendagelengthandexternalreproductiveorgans.Anotherexampleisthelaterlarvalstageofcrabs(big-eyedlarvae),whichhavethesameheadandthoraxastheadult,butthewideabdomenhasnotyetbeenbentunderit.
Duetothedifferentevolutionaryprocess,theembryonicperiodofinvertebratesisshorterthanthatofvertebrates,butthedevelopmentalstagesareobvious.Similarly,withineachphylumofinvertebrates,thelowertheevolutionarylevelofthespecies,theshortertheembryonicdevelopmentprocess,themoreobviousthevariousdevelopmentstages;theearlierthelarvaeappear,thelongerthedurationis,sothesystemdevelopmentstagesTheclearerthereflection.
Theembryonicdevelopmentofinvertebratesisthesameasthatofvertebrates:biosynthesisandcelldifferentiationarealsocarriedoutsequentiallyinstages;fromtissuegenerationtoorganogenesis,andfinallyfunctionaldifferentiationbasedontheestablishmentofmorphology.Theaboveprocessisnotonlyrealizedthroughtheinteractionbetweencellsandtissues,butalsomusthavecertainenvironmentalconditions.Forexample,light,droughtandcoldhaveadirectimpactonthemoltinganddiapauseofembryosorlarvae,andthephysicalandchemicalpropertiesofthesubstrateAndbiologicalfactorscandeterminethesettlement,attachmentandmetamorphosisofaquaticlarvae,andconditionssuchasnutrition,salinity,temperature,light,spaceandpheromonecanaffecttheoccurrenceanddifferentiationofgonads.
Ihmisen
Ihmisenfertilizationisdoneintheupperpartofthefallopiantube.Whenthefertilizedeggisinthemiddleofthefallopiantube,embryonicdevelopmentbegins.Thefertilizedeggcleavageswhiledescendingalongthefallopiantubetowardtheuterus,reachingtheuterusin2to3days.Theembryoatthattimewasasmallhollowspheremadeupofmanycells,calledablastocyst.
Aboutoneweekafterfertilization,theblastocystimplantsinthethickenedendometrium,whichiscalledpregnancy.Theblastocystcontinuestogrowthroughcelldivisionandcelldifferentiation,andisdividedintotwoparts.Onepartoftheembryoitselfwilldevelopintoafetus;theotherpartwillevolveintotheepiembryonicmembrane,themostimportantofwhichistheamnioticmembrane,placentaandumbilicalcord.Thefetusexchangessubstanceswiththemotherthroughtheplacenta.
Inthefirsttwomonths,theembryocontinuestodivideanddifferentiate,producevariouscells,andformvarioustissuesandorgans.Thisistheimmatureandsensitiveperiodofdevelopmentandresistancetovariousexternalstimuli.Theabilityandadaptabilityareverypoor,sopaygreatattentiontosafety,includingpregnantwomentakingmedication,receivingradiationorexposuretootherharmfulfactors,etc.,willaffectthenormaldevelopmentofthefetus;bytheendofthethirdmonth,allorgansystemsarebasicallycompletedandhavebeencalledthefetus.
Inthefuture,itismainlyduetoenlargementandafewstructuralchanges.Atthistime,theresistanceisenhanced,butifyoudonotpayattention,miscarriagecanstilloccur;afterthe5thmonth,itissafer.Duetotherapidgrowthofthefetus,theburdenonthemotherisincreasing;itusuallytakesabout280days,whichisalittlemorethanninemonths(itisoftensaidthat"pregnancyinOctober"isactuallynotaccurate),andnaturalchildbirthwilloccur.
Perusmalli
Directdevelopmentandindirectdevelopment,astwomodels,althoughtheycansummarizetheembryonicdevelopmentofallmulticellularanimals,theyarenotenoughtoexpresstheembryosofinvertebrates.Thecharacteristicsofdevelopmentandtheirinterrelationships.Themorphogenesisoflaterembryonicdevelopmentormetamorphosisofinvertebratesineachphylumhasitsowndevelopmentdirection,andofcourseitisdifficulttosummarizeitintoafewmodels.However,iftheearlyembryonicdevelopmentprocessprevails,therearesomecommonalitiesorregularitiesinmorphogenesisnomatterbetweencategorieswithsimilarevolutionarylevelsorbetweencategorieswithdifferentevolutionarylevels.Thisaspectnotonlyreflectsthemutualrestrictionbetweenindividualdevelopmentandphylogeny,butalsoreflectsthelevelofevolutionarystatus,butalsoreflectsthedistanceofkinship.Sincethe1940s,theabovecontenthasbecomeanimportantbasisfordeterminingtheclassificationpositionofvariousinvertebratesandexplainingtheirevolutionarydirection,sohereisalsousedasatheoreticalbasisforestablishingthebasicmodelofinvertebrateembryonicdevelopment.Inadditiontotheprotozoanmodelandthetwo-germanimalmodel,thefollowingbasicmodelsofembryonicdevelopmentareconsistentwiththeclassificationofcoelentia,prostheticcoelentia,cleftcoelenterateandcoelenterate.Ihmisenfertilizationisdoneintheupperpartofthefallopiantube.Whenthefertilizedeggisinthemiddleofthefallopiantube,embryonicdevelopmentbegins.Thefertilizedeggundergoesmitosiswhiledescendingalongthefallopiantubetowardtheuterus,anditcanreachtheuterusin2to3days.Theembryoatthattimewasasmallhollowspheremadeupofmanycells,calledablastocyst.
Aboutoneweekafterfertilization,theblastocystimplantsinthethickenedendometrium,whichiscalledpregnancy.Theblastocystcontinuestogrowthroughcelldivisionandcelldifferentiation,andisdividedintotwoparts.Onepartoftheembryoitselfwilldevelopintoafetus;theotherpartwillevolveintotheepiembryonicmembrane,themostimportantofwhichistheamnioticmembrane,placentaandumbilicalcord.Thefetusexchangessubstanceswiththemotherthroughtheplacenta.
Inthefirsttwomonths,theembryocontinuestodivideanddifferentiate,producevariouscells,andformvarioustissuesandorgans.Thisistheimmatureandsensitiveperiodofdevelopmentandresistancetovariousexternalstimuli.Theabilityandadaptabilityareverypoor,sopaygreatattentiontosafety,includingpregnantwomentakingmedication,receivingradiationorexposuretootherharmfulfactors,etc.,willaffectthenormaldevelopmentofthefetus;bytheendofthethirdmonth,allorgansystemsarebasicallycompletedandhavebeencalledthefetus.
Inthefuture,itismainlyduetoenlargementandafewstructuralchanges.Atthistime,theresistanceisenhanced,butifyoudonotpayattention,miscarriagecanstilloccur;afterthe5thmonth,itissafer.Duetotherapidgrowthofthefetus,themother’sburdenisincreasing;itusuallytakesabout280days,whichisalittlemorethanninemonths(itisoftensaidthat"pregnancyinOctober"isactuallymeasuredbythelunarcalendar),andnaturalchildbirthwilloccur
Alkueläimet
Theprotozoahasasimplestructureandrapidgeneration.Usuallyonlytheterm"reproduction"isusedtosummarizeitsontogeny.Infact,thereproductiveprocessofthiskindofanimalsisalsodifferent.Singleschizophreniaisthesimplest,whilesexualreproductionandgenerationalalternationaremorecomplicated.Theentireprocessofthelattertwoisoftencalledlifehistoryordevelopmentalloop.Theimportantthingisthattherearealsotransitionalformsinthedevelopmentalring,causingtheontogenyofprotozoaandmulticellularanimalstohavesomethingincommon.
Theasexualreproductionofprotozoaisaccomplishedthroughthedirectdivisionofindividuals.Includingtwobasicformsoftwosplitsanddoublesplits.Forexample,inthedoublesplittingofredcoccidia,theflagellaisfirstlostandthecellshellissecretedonthecellsurface,andthewormbodyinsidetheshellbecomesasporoblast.Thiscelldividestwiceinto4daughtercells.Thelatterarecalledmigratorysporesaftertheygivebirthtoflagella.Asaresult,thesporesgrowintonewindividuals.Sporoblastsandlaterdaughtercellsareequivalenttotheembryonicstageintheindividualdevelopmentofmulticellularanimalsbecauseoftheirmorphologicaldifferencesfromtheparentbody.
Varhainen karja
Understandthemaincharacteristicsoftheearlyembryonicdevelopmentoflivestockfromcleavagetotheformationofthreegermlayers.
a. Fertilizedegg-malliNo.1
b. Pilko — mallit 2, 3, 4, 5 ja 6
Differenttimecleavage,thenumberofblastomerecellsincreases,andtheyarestilldividinginthezonapellucida.
c. Blastocyst-malli 7,8,9
Blastocystcavity,innercellmass,blastocystandimplantationappeared.
d. Gastrulaatio – mallinumerot 10, 11 ja 12
Gergut, gastrulaatio, gastrulaatio, ektoderma, endoderma.
e.Mesodermformation – mallit13,14,15,16
Alkuperäiset viivat,mesoderma;atthesametime,notochord.
Tri-dermaalinen erilaistuminen (alkionsisäinen osa) malliNo.17-24
Neuroblastit
Kehitysteoria
Gradualtheoryh3>
AlmostacenturyafterHippocrates,theancientGreekphilosopherAristotle(Macedo-nianAristotle,384to322before)systematicallystudiedembryonicdevelopment.Accordingtoaseriesofobservationsonthedevelopmentofinvertebrates,hebelievesthatthedevelopmentofchickenembryosisgraduallyformedfromsimpletocomplex,andcalleditthetheoryofevolutionorepigenesis.Thisisanaivematerialistview,butatthesametimehebelievesthattheinternalforcethatdrivesembryonicdevelopmentisthesoul,whichleadstotheoccurrenceofindividualssimilartoit.Obviouslythisisanidealisticview.Nevertheless,Aristotle'sthesisonembryonicdevelopmenthasbeenacceptedbypeopleforaslongas2,000years.
Esimuodostusta edeltävä teoria
Aristotle’sviewthatembryonicdevelopmentissoul-drivenisalsotheprototypeofpre-formationorpre-formation,soheproposedThesetwocontradictoryandopposingviewshavehadaprofoundimpactonthestudyofembryonicdevelopment.Untilthelatterpartofthe17thcentury,withthediscoveryofthemicroscope,AntonivanLeeuwenhoek(1632-1723)observedhumanspermatozoaandproposedthetheoryofspermatozoa.HebelievedthatpreformedUyghursexistedinspermatozoa.Somepeopleevenclaimedtohaveseenanembryointhesperm,andaminiaturefigureappeared(Figure1).Duringdevelopment,theminiaturepeopleonlyneedtostretchoutandgrowup.AnotherrepresentativeofthepreformedviewistheembryologistMarcelloMal-pighi(1637-1680),Swammerdam(JanSwammerdam)andGraaf(R.Graaf),whodiscoveredhumansThefolliclesintheovarywerecarefullyobserved,andadelicatepictureofthechickenembryowasdrawn.Itwasfoundthattherewerebutterfly-likeadultsinthepupaeofinsects.Therefore,theybelievethattheembryoalreadyexistsintheeggcellbeforehand,andthatdevelopmentisnothingmorethancontinuedgrowth.Thisisthepre-formationofembryogenesis.Sincethen,manyfamousbiologistshavebeenprogressive,includingthefamousKarlErnstVonBaer(1792-1876).Aftercomparingtheembryonicdevelopmentofvariousvertebrates,heproposedthatallvertebratesonlyundergodifferentiationofdevelopmentalpathwaysafterpassingaverysimilarembryonicstage,whichisthefamousvonBell'slaw.TheextremeofthepreformationtheoryisCh.Bonnet'ssuittheory,whichholdsthattherearesmallerembryosintheembryo,justlikeaRussianmatryoshka.Thelargeembryocontainsthesmallembryo,andthesmallembryocontainsthesmallerembryo..Thepreformationtheorydominatedinthe17thand18thcenturies,whichmayberelatedtothedominantroleofmechanistictheoryinthephilosophicalworldatthattime.Inthe18thcentury,thetwoschoolsofpre-formationandpost-formationwerearguing.Inthe19thcentury,afterthecelltheorywasputforward,thepreformationtheorygraduallyfelloutoffavorandevendisappeared.Themajorityofembryologistsagreedwiththeviewsandideasoftheevolutionarytheory,andthiscontroversywasresolved.
AnimalEmbryoProcess
Althoughtherearemanytypesofanimals,embryodevelopmentstillhasasimilarprocess,whichcanbedividedintofertilization,cleavage,morula,blastocyst,gastrulaandStagesoforganformation.Inaddition,duringtheembryonicdevelopmentofvertebrates,thecommonfeaturesofvariousanimalswillappearfirst(suchasskin),andthenspecializedstructures(suchasfishscales)willgraduallydevelop,andthereisadifferencebetweenmorecomplexspeciesandmoreprimitivespecies.Itwasquitesimilaratthebeginning,andthengraduallyincreasedthevariationwiththedevelopmenttime.
Lannoitus
Therearesomemantlesaroundthecellmembraneoftheegg.Thefirstlayeriscomposedofglycoproteins.Itisgenerallycalledvitellinemembrane(eggcellmembrane).Inmammals,itiscalledeggSheath(zonapellucida).Whenaspermenterstheegg,theeggsofmostspecieswillformaprotection,sothatotherspermcannolongerentertheegg.Afewspecies,suchascertainbirdsandreptiles,althoughallowotherspermtoenter,thereisstillonlyonespermthatcaninteractwiththenucleusoftheegg.Thenucleusofthespermandeggwillfuseandformafertilizedeggwithadoublesetofchromosomes.
Incloningtechnology,theprocessofreplacingfertilizationistoremovethenucleusoftheegg,andthenimplantthesomaticcellintotheegg.Animalsundergoingasexualreproductionusuallydonotneedcellfusion,butdirectlyproducelarvaethroughbuddingordivisionreproduction.
Theprocessoffertilizationisroughlyasfollows:thesecondaryoocytesneedtodeveloptothemiddlestageofthesecondmeioticdivisionbeforetheycanbefertilized.Afterthecapacitatedspermmeetsthesecondaryoocyteofthisperiod.Theacrosomereactionoccurs,releasingacrosomeenzyme,dissolvingthesubstancebetweenthecumuluscells,formingachannel.Subsequently,contactwiththezonapellucida,acrosindissolvesoutachannelagaininthezonapellucida.Spermcontactstheyolkmembranethroughthetwochannelsdissolvedbyacrosin,andthezonapellucidareactionoccursimmediatelytopreventotherspermfrompassingthroughthezonapellucida.Thisisthefirstbarriertopreventmultiplespermfromenteringtheeggcell.Afterthespermcontactsthevitellinemembrane,itisentangledbyalargenumberofmicrovillionitssurface.Subsequently,thespermoutermembraneandthevitellinemembranefuse(usingthefluidityofthecellmembrane),thesperm'stailfallsoff,andthenucleusenterstheeggcell.Afterthespermenterstheegg,theeggcellimmediatelyundergoesyolkmembranesealing(eggcellmembranereaction)(thesecondbarriertopreventpolyspermia)andisactivatedforthesecondmeioticdivision,expellingthesecondpolarbody.Atthesametime,thenuclearmembraneofthespermruptures,formingalargernucleus,calledthemalepronucleus.Thenucleusformedbytheeggcellafterthesecondmeiosisiscalledthefemalepronucleus(usuallythemalepronucleusislargerthanthefemalepronucleus).Thetwopronucleiareclosetoeachotherandfusewitheachother,andfinallyadiploid(forhumansandmostmammals)zygoteisformed,andthefertilizationprocessisbasicallycompleted.Note:Thefertilizationprocessiscompletedinthefallopiantube.
pilkkominen
Thecombinationofspermandeggwillformafertilizedegg.Duetotheasymmetricaldistributionoftheyolk,thefertilizedeggcanbedividedintoanimalpoles(whichwilldevelopintoectoderm).)Andplantpoles(willdevelopintomesodermandendoderm).Duringthecleavageperiod,thefertilizedeggwillfirstdivideintotwocells,andthenthecellswillusuallydoubleoneafteranother.However,formammals,sometimesitwilldivideatdifferenttimesandcauseonlyanoddnumberofcells.Atthisstage,thetotalvolumeoftheembryoisroughlythesame.
Thestageinwhichcellsdivideinto16to32cellsiscalledmorula.Atthisstage,thedivisionfrequencyoftheanimalpolewillsurpassthatofthecellgroupthatisclosetotheplantpoleandhasayolk.Atthestagewherethenumberofcellsexceeds32,itiscalledablastula.Ablastulacavityisformedintheblastulaneartheanimalpole.
Differentspecieshavedifferentwaysofcleavage,whichcanbedividedintoholoblasticcleavegeandmeroblasticcleavage,whichcanbesubdividedintomanydifferentways.Suchasradiationcleavageandspiralcleavageininvertebrates,androtationaldivisionofmammals.
· Täydellinen pilkkominen
Radiaali (merisammakkoeläimet)
Kahdenväliset (hännät, sammakkoeläimet))
Spiraali (annelidit, nilviäiset)
pyörivä (nisäkkäät)
· Epätäydellinen pilkkominen
p>Discoidal (kalat, linnut, matelijat)
Pinnallinen (hyönteinen)
gastrualembryo
Afterthecelldividesintoablastocyst,itundergoesaprocesscalledgastrulationandformsagastrulation.Therearemanydifferentwaysofformingthegastrulation,whichcanberoughlydividedinto5types:Invagination-Thecellsoftheplantpolearerecessedintotheembryo,andfinallypassthroughtheembryotoopenattheotherend.ItisworthnotingHowever,theopeningthatappearedlaterwillbecomethemouthoftheanimal,andtheoriginaldepressionwillbecometheanus.Thisiswhytheposterioranimalgetsitsname,suchastheendodermoftheseaurchin.
·Involution-Theplantpolecellsproliferateinwardalongtheinnerwalloftheblastocystcavity,whiletheexteriorisreplacedbyanimalpolecells,suchasthemesodermoffrogs.
·Ingression-Afterdividingcellsinaspecificplace,theymovetootherspecificlocations,suchasthemesodermofseaurchinsandtheneuroblastsofDrosophila.
·Delamination-thecellsintheouterlayerslide.Originally,onlyonelayerofcellsproliferateintotwolayers,suchasthehypoblastsofmammalsandbirds.
·Epiboly-Cellsintheouterlayerexpand,squeezetowardthedepressionoftheplantpole,andgraduallymovetotheinnerwalloftheblastocystcavitytoformtwolayers,suchastheectodermoffrogsandseaurchins.
Animalembryosusethesefivemethodstoformacombinationofectoderm,mesodermandendoderm,andthesethreegermlayerswillthenformvariouscells.Forexample,developedfromthemesoderm,thepluripotentmesenchymalcellscandifferentiateintofibroblasts,chondroblasts,scleroblasts,adipocytes,smoothmusclecells,rhabdomyoblasts,hematopoieticcells,andsoon.
Organisaatio
Theprocessofformingvarioustissuesandorgansfromectoderm,mesodermandendodermiscalledorganogenesis,alsoknownasorganogenesis.Takethefrogembryoasanexample.Intheearlystageoforganformation,theectodermwillsaginwardaftertheprotrusion,forminganeuralridgeandaneuraltube;themesodermwillformasomiteandaspine,andthespacesurroundedbymesodermalsegmentsiscalledForthebodycavity.
Ihmisen EmbryoProcess
Ihmisendevelopmentisgenerallylessthan8weeksforembryos,andmorethan8weeksforembryos.
1 kuukausi
Oncethefertilizedeggisformed,thecleavagemechanismisinitiatedimmediately.Onthe3rdand4thday,thefertilizedegghaddividedintoaninnercellmassofabout100cells.Theperistalticcellclustersaresentintotheuterinecavitythroughthefallopiantube,andadheretotheendometriumthroughthesurfacemucus.Thecellsclosetotheendometriumsecreteanenzymetolysetheendometrialcellstoformasmallhole.Fromthe5thand6thdaystothe11thand12thdays,theentireblastocystisembeddedintheinnermembrane.Thisprocessiscalled"implantation"or"implantation"(Figure1-6).Aftertheimplantationoftheblastocyst,theendometriumre-grows,andthetrophoblastcellsonthesurfaceoftheblastocystcontinuetodivide,growvilli-likeprotrusions,andformmanyvilli,whichextendintotheendometriumtoabsorbmaternalnutrition(Figure1).
2 kuukautta
Theembryoisaflatdisc,calledtheblastoderm,withadiameterofabout2cm,floatingintheamnioticcavity.Atthistime,thethreegermlayersoftheembryohaveformed,andStarttodifferentiate.Exceptfortheplacentawherethevillidonotfalloff,thevilliaroundtheblastocystallfalloffandthesurfacebecomessmooth(Figurea).Theembryoisformedbytheremainingblastocystvilliandtheendometrium,andtheplacentaisnotfullyformeduntilthe12thweekoftheembryo.Atthe6thweek,aheartprimordiumwithtwochannelsmerged.Althoughitdoesnothaveaheartshape,ithasalreadybeguntobeat.Afterthat,aclosedcirculatingbloodvesselgraduallyappearedintheembryo,andtheembryobegantoproduceitsownblood(includingvariousbloodcells).Atthe7thweek,theneuraltubeappeared,thebackpartformedthespinalcord,andthefrontpartwasslightlyenlarged,whichwastheprimordiumofthebrain(Figurec).Atthe8thweek,theembryoisabout20mmlong.Theheartpresentsasmallprotrusionontheventralsideandbeatsgently.Atthistime,therearenolimbs,onlyasmalltailprotrudingbehind.
3 kuukautta
Thefetusgrowsarmsfirst,andthenlegs.Theheadandtailarebenttogether.Theheadhasears,nostrilsandchin.Theheadisaboutthelengthofthebody.1/3.Ovalhandsandfeetappearinthe11thweek,andfivedeeplineswillformfingers(toes).Twoeyesgrowonbothsidesofthehead,lipsandgumsappear,andthetaildisappears.Intheearlystageofembryonicdevelopment,thefetusdevelopsrapidly,andtheprimordiaofallorganshavebasicallybeenformedinthesecondandthirdmonths.Afterthat,onlyinternalcellsproliferatetoincreasetheirvolume.
4 kuukautta
Fetalsexorgansappear,theeyesareturnedtothefrontoftheface,theforeheadisprominent,thenostrilsareopen,theearsarevisible,thelimbsbecomelonger,thefingersareidentifiableandtherearefingers(nail.Theheadandneckcanbeturnedandthemouthwillswallowamnioticfluid.
5 kuukautta
Thefetusisabout25cmlong,weighs250g,andtheheadaccountsfor1/4ofthebodylength.Lanugohairandhairappearontheskin,sebaceousglandsandsweatglandsappear;therearefetusesintheintestinesFecesaccumulate,mainlybiledischargedfromthegallbladder.Thekidneyscanurinate,theurineisdischargedintotheamnioticfluid,andthefetus'slimbscanmove.
6 kuukautta
Thefetusisabout30cmlongandweighs600-750g.Thefetusisrecognizable,thelungsbegintodevelop,thehairincreases,andtherearefatandwrinklesundertheskin.Thefetalheartrateis120-160beatsperminuteandcanbeheardwithanordinarystethoscope.Thefetuscanhearsounds,suchascarhornsandparentalconversations.
7 kuukautta
Thefetusis35cmlongandweighs1,000-1,200g.Thebrainhasasulcusandcorticalstructure.However,thenumberandvolumeofbraincellshaveyettoincrease,nervefibersarenotlongenough,bonesandmusclesaredeveloping,andtheskull,spine,ribs,andlimbbonescanbeseenunderX-rays,becauseatthistimeboneshavebeguntocalcifyandjointsareclearlyvisible.Thefunctionofinternalorgansisgraduallyimproved,andhecanbreatheandcry.Theskinisredwithmanywrinkles,becausethereistoolittlesubcutaneousfat,itisdifficulttomaintainbodytemperatureifbornatthistime.
8 kuukautta
Becausethemuscleshavebeendeveloped,andtheinterconnectionbetweenthenervecentersmakesthefetalmovementaqualitativechange.Atthistime,itwillnotonlypunchandkick,butalsoturnleftandrightormakea180or360degreeturn,whichwillwakeupthemotherfromthedream.Theeyesofthefetuscanbeopened,andthesurfaceoftheeyeballsisprotectedbyafilm.
9 kuukautta
Sikiö on 45-47 cm pitkä ja painaa 2 000-2 300 g.Tässä kuussa syntyneiden eloonjäämisaste voi olla jopa 95%. Ihonalainen rasva kasvaa, ryppyjä häviää vähitellen, ihonvaaleanpunaiset ja kiharat hiukset katoavat.
10 kuukautta
Sikiö on noin 50 cm pitkä, painaa noin 3 000 g,sisältää ihonalaista rasvaa ja on suojattu kahdella kuukaudella selkä- ja nivelet. Hiukset paksut, suorat ja kiiltävät, kynnet (varpaat) ulottuvat sormien (varpaiden) päiden yli ja jalanjälkien pohjassa.
Läpimurto
InApril2016,mycountryrealizedthedevelopmentofmammalianembryosinspaceforthefirsttime,andthiswasthefirsttimeintheworldthatmammalianembryosdevelopedinspace.