Ембрионално развитие

Етапи на развитие

Безгръбначни

Безгръбначниincludemorethan30phyla,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.

Човек

Човекfertilizationisdoneintheupperpartofthefallopiantube.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.

Основен модел

Directdevelopmentandindirectdevelopment,astwomodels,althoughtheycansummarizetheembryonicdevelopmentofallmulticellularanimals,theyarenotenoughtoexpresstheembryosofinvertebrates.Thecharacteristicsofdevelopmentandtheirinterrelationships.Themorphogenesisoflaterembryonicdevelopmentormetamorphosisofinvertebratesineachphylumhasitsowndevelopmentdirection,andofcourseitisdifficulttosummarizeitintoafewmodels.However,iftheearlyembryonicdevelopmentprocessprevails,therearesomecommonalitiesorregularitiesinmorphogenesisnomatterbetweencategorieswithsimilarevolutionarylevelsorbetweencategorieswithdifferentevolutionarylevels.Thisaspectnotonlyreflectsthemutualrestrictionbetweenindividualdevelopmentandphylogeny,butalsoreflectsthelevelofevolutionarystatus,butalsoreflectsthedistanceofkinship.Sincethe1940s,theabovecontenthasbecomeanimportantbasisfordeterminingtheclassificationpositionofvariousinvertebratesandexplainingtheirevolutionarydirection,sohereisalsousedasatheoreticalbasisforestablishingthebasicmodelofinvertebrateembryonicdevelopment.Inadditiontotheprotozoanmodelandthetwo-germanimalmodel,thefollowingbasicmodelsofembryonicdevelopmentareconsistentwiththeclassificationofcoelentia,prostheticcoelentia,cleftcoelenterateandcoelenterate.Човекfertilizationisdoneintheupperpartofthefallopiantube.Whenthefertilizedeggisinthemiddleofthefallopiantube,embryonicdevelopmentbegins.Thefertilizedeggundergoesmitosiswhiledescendingalongthefallopiantubetowardtheuterus,anditcanreachtheuterusin2to3days.Theembryoatthattimewasasmallhollowspheremadeupofmanycells,calledablastocyst.

Inthefuture,itismainlyduetoenlargementandafewstructuralchanges.Atthistime,theresistanceisenhanced,butifyoudonotpayattention,miscarriagecanstilloccur;afterthe5thmonth,itissafer.Duetotherapidgrowthofthefetus,themother’sburdenisincreasing;itusuallytakesabout280days,whichisalittlemorethanninemonths(itisoftensaidthat"pregnancyinOctober"isactuallymeasuredbythelunarcalendar),andnaturalchildbirthwilloccur

Протозои

Theprotozoahasasimplestructureandrapidgeneration.Usuallyonlytheterm"reproduction"isusedtosummarizeitsontogeny.Infact,thereproductiveprocessofthiskindofanimalsisalsodifferent.Singleschizophreniaisthesimplest,whilesexualreproductionandgenerationalalternationaremorecomplicated.Theentireprocessofthelattertwoisoftencalledlifehistoryordevelopmentalloop.Theimportantthingisthattherearealsotransitionalformsinthedevelopmentalring,causingtheontogenyofprotozoaandmulticellularanimalstohavesomethingincommon.

Theasexualreproductionofprotozoaisaccomplishedthroughthedirectdivisionofindividuals.Includingtwobasicformsoftwosplitsanddoublesplits.Forexample,inthedoublesplittingofredcoccidia,theflagellaisfirstlostandthecellshellissecretedonthecellsurface,andthewormbodyinsidetheshellbecomesasporoblast.Thiscelldividestwiceinto4daughtercells.Thelatterarecalledmigratorysporesaftertheygivebirthtoflagella.Asaresult,thesporesgrowintonewindividuals.Sporoblastsandlaterdaughtercellsareequivalenttotheembryonicstageintheindividualdevelopmentofmulticellularanimalsbecauseoftheirmorphologicaldifferencesfromtheparentbody.

Ранно животновъдство

Understandthemaincharacteristicsoftheearlyembryonicdevelopmentoflivestockfromcleavagetotheformationofthreegermlayers.

а.Оплодено яйце-модел№1

б. Разцепване—модели 2,3,4,5 и6

Differenttimecleavage,thenumberofblastomerecellsincreases,andtheyarestilldividinginthezonapellucida.

c.Бластоциста-модел7,8,9

Blastocystcavity,innercellmass,blastocystandimplantationappeared.

d. Гаструлация—Модели № 10, 11 и 12

Гергут, гаструлация, гаструлация, ектодерма, ендодерма.

д. Образуване на мезодерма—модели 13,14,15,16

Embryonic development

Примитивни ивици, мезодерма; в същото време, нотохорда.

Три-дермална диференциация (интраембрионална част) модел № 17-24

Невробласти

Теория на развитието

Gradualtheoryh3>

AlmostacenturyafterHippocrates,theancientGreekphilosopherAristotle(Macedo-nianAristotle,384to322before)systematicallystudiedembryonicdevelopment.Accordingtoaseriesofobservationsonthedevelopmentofinvertebrates,hebelievesthatthedevelopmentofchickenembryosisgraduallyformedfromsimpletocomplex,andcalleditthetheoryofevolutionorepigenesis.Thisisanaivematerialistview,butatthesametimehebelievesthattheinternalforcethatdrivesembryonicdevelopmentisthesoul,whichleadstotheoccurrenceofindividualssimilartoit.Obviouslythisisanidealisticview.Nevertheless,Aristotle'sthesisonembryonicdevelopmenthasbeenacceptedbypeopleforaslongas2,000years.

Предварителна теория на формирането

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.

Оплождане

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.

Деколте

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.

· Пълно разцепване

Радиални (мишки, земноводни)

Двустранно (опашки, земноводни))

Спирала (анелиди, мекотели)

ротационен (бозайници)

· Непълно разцепване

Дискоиден (риби, птици, влечуги)

Повърхностно (насекомо)

гаструален ембрион

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.

Образуване на органи

Theprocessofformingvarioustissuesandorgansfromectoderm,mesodermandendodermiscalledorganogenesis,alsoknownasorganogenesis.Takethefrogembryoasanexample.Intheearlystageoforganformation,theectodermwillsaginwardaftertheprotrusion,forminganeuralridgeandaneuraltube;themesodermwillformasomiteandaspine,andthespacesurroundedbymesodermalsegmentsiscalledForthebodycavity.

ЧовекEmbryoProcess

Човекdevelopmentisgenerallylessthan8weeksforembryos,andmorethan8weeksforembryos.

1 месец

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 месеца

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 месеца

Thefetusgrowsarmsfirst,andthenlegs.Theheadandtailarebenttogether.Theheadhasears,nostrilsandchin.Theheadisaboutthelengthofthebody.1/3.Ovalhandsandfeetappearinthe11thweek,andfivedeeplineswillformfingers(toes).Twoeyesgrowonbothsidesofthehead,lipsandgumsappear,andthetaildisappears.Intheearlystageofembryonicdevelopment,thefetusdevelopsrapidly,andtheprimordiaofallorganshavebasicallybeenformedinthesecondandthirdmonths.Afterthat,onlyinternalcellsproliferatetoincreasetheirvolume.

4 месеца

Fetalsexorgansappear,theeyesareturnedtothefrontoftheface,theforeheadisprominent,thenostrilsareopen,theearsarevisible,thelimbsbecomelonger,thefingersareidentifiableandtherearefingers(nail.Theheadandneckcanbeturnedandthemouthwillswallowamnioticfluid.

5 месеца

Thefetusisabout25cmlong,weighs250g,andtheheadaccountsfor1/4ofthebodylength.Lanugohairandhairappearontheskin,sebaceousglandsandsweatglandsappear;therearefetusesintheintestinesFecesaccumulate,mainlybiledischargedfromthegallbladder.Thekidneyscanurinate,theurineisdischargedintotheamnioticfluid,andthefetus'slimbscanmove.

6 месеца

Thefetusisabout30cmlongandweighs600-750g.Thefetusisrecognizable,thelungsbegintodevelop,thehairincreases,andtherearefatandwrinklesundertheskin.Thefetalheartrateis120-160beatsperminuteandcanbeheardwithanordinarystethoscope.Thefetuscanhearsounds,suchascarhornsandparentalconversations.

7 месеца

Thefetusis35cmlongandweighs1,000-1,200g.Thebrainhasasulcusandcorticalstructure.However,thenumberandvolumeofbraincellshaveyettoincrease,nervefibersarenotlongenough,bonesandmusclesaredeveloping,andtheskull,spine,ribs,andlimbbonescanbeseenunderX-rays,becauseatthistimeboneshavebeguntocalcifyandjointsareclearlyvisible.Thefunctionofinternalorgansisgraduallyimproved,andhecanbreatheandcry.Theskinisredwithmanywrinkles,becausethereistoolittlesubcutaneousfat,itisdifficulttomaintainbodytemperatureifbornatthistime.

8 месеца

Becausethemuscleshavebeendeveloped,andtheinterconnectionbetweenthenervecentersmakesthefetalmovementaqualitativechange.Atthistime,itwillnotonlypunchandkick,butalsoturnleftandrightormakea180or360degreeturn,whichwillwakeupthemotherfromthedream.Theeyesofthefetuscanbeopened,andthesurfaceoftheeyeballsisprotectedbyafilm.

9 месеца

Плодът е дълъг 45-47 см и тежи 2000-2300 г. Процентът на преживяемост на плода, родени през този месец, може да бъде 95%.

10 месеца

Плодът е дълъг около 50 см, тежи около 3000 г, богат е на подкожна мазнина и е защитен от себум на гърба и ставите. Косата е дебела, права и лъскава, ноктите (пръстите на краката) се простират отвъд краищата на пръстите (пръстите на краката) и стъпалата на краката имат повече отпечатъци от длани.

Пробив

InApril2016,mycountryrealizedthedevelopmentofmammalianembryosinspaceforthefirsttime,andthiswasthefirsttimeintheworldthatmammalianembryosdevelopedinspace.