Vývojová stadia
Bezobratlí
Bezobratlíincludemorethan30phyla,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.
Člověk
Člověkfertilizationisdoneintheupperpartofthefallopiantube.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.
Základní model
Directdevelopmentandindirectdevelopment,astwomodels,althoughtheycansummarizetheembryonicdevelopmentofallmulticellularanimals,theyarenotenoughtoexpresstheembryosofinvertebrates.Thecharacteristicsofdevelopmentandtheirinterrelationships.Themorphogenesisoflaterembryonicdevelopmentormetamorphosisofinvertebratesineachphylumhasitsowndevelopmentdirection,andofcourseitisdifficulttosummarizeitintoafewmodels.However,iftheearlyembryonicdevelopmentprocessprevails,therearesomecommonalitiesorregularitiesinmorphogenesisnomatterbetweencategorieswithsimilarevolutionarylevelsorbetweencategorieswithdifferentevolutionarylevels.Thisaspectnotonlyreflectsthemutualrestrictionbetweenindividualdevelopmentandphylogeny,butalsoreflectsthelevelofevolutionarystatus,butalsoreflectsthedistanceofkinship.Sincethe1940s,theabovecontenthasbecomeanimportantbasisfordeterminingtheclassificationpositionofvariousinvertebratesandexplainingtheirevolutionarydirection,sohereisalsousedasatheoreticalbasisforestablishingthebasicmodelofinvertebrateembryonicdevelopment.Inadditiontotheprotozoanmodelandthetwo-germanimalmodel,thefollowingbasicmodelsofembryonicdevelopmentareconsistentwiththeclassificationofcoelentia,prostheticcoelentia,cleftcoelenterateandcoelenterate.Člověkfertilizationisdoneintheupperpartofthefallopiantube.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
Prvoci
Theprotozoahasasimplestructureandrapidgeneration.Usuallyonlytheterm"reproduction"isusedtosummarizeitsontogeny.Infact,thereproductiveprocessofthiskindofanimalsisalsodifferent.Singleschizophreniaisthesimplest,whilesexualreproductionandgenerationalalternationaremorecomplicated.Theentireprocessofthelattertwoisoftencalledlifehistoryordevelopmentalloop.Theimportantthingisthattherearealsotransitionalformsinthedevelopmentalring,causingtheontogenyofprotozoaandmulticellularanimalstohavesomethingincommon.
Theasexualreproductionofprotozoaisaccomplishedthroughthedirectdivisionofindividuals.Includingtwobasicformsoftwosplitsanddoublesplits.Forexample,inthedoublesplittingofredcoccidia,theflagellaisfirstlostandthecellshellissecretedonthecellsurface,andthewormbodyinsidetheshellbecomesasporoblast.Thiscelldividestwiceinto4daughtercells.Thelatterarecalledmigratorysporesaftertheygivebirthtoflagella.Asaresult,thesporesgrowintonewindividuals.Sporoblastsandlaterdaughtercellsareequivalenttotheembryonicstageintheindividualdevelopmentofmulticellularanimalsbecauseoftheirmorphologicaldifferencesfromtheparentbody.
EarlyLivestock
Understandthemaincharacteristicsoftheearlyembryonicdevelopmentoflivestockfromcleavagetotheformationofthreegermlayers.
a.Fertilizedegg-modelNo.1
b. Štěpení – modely 2, 3, 4, 5 a 6
Differenttimecleavage,thenumberofblastomerecellsincreases,andtheyarestilldividinginthezonapellucida.
c.Blastocyst-Model7,8,9
Blastocystcavity,innercellmass,blastocystandimplantationappeared.
d. Gastrulation – Model č. 10, 11 a 12
Gergut, gastrulace, gastrulace, ektoderm, endoderm.
e.Mezodermace – modely13,14,15,16
Primitivní pruhy, mezoderm; současně, notochord.
Tridermální diferenciace (intraembryonální část) model č. 17-24
Neuroblasty
Vývojová teorie
Gradualtheoryh3>
AlmostacenturyafterHippocrates,theancientGreekphilosopherAristotle(Macedo-nianAristotle,384to322before)systematicallystudiedembryonicdevelopment.Accordingtoaseriesofobservationsonthedevelopmentofinvertebrates,hebelievesthatthedevelopmentofchickenembryosisgraduallyformedfromsimpletocomplex,andcalleditthetheoryofevolutionorepigenesis.Thisisanaivematerialistview,butatthesametimehebelievesthattheinternalforcethatdrivesembryonicdevelopmentisthesoul,whichleadstotheoccurrenceofindividualssimilartoit.Obviouslythisisanidealisticview.Nevertheless,Aristotle'sthesisonembryonicdevelopmenthasbeenacceptedbypeopleforaslongas2,000years.
Předformační teorie
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.
Animal EmbryoProcess
Althoughtherearemanytypesofanimals,embryodevelopmentstillhasasimilarprocess,whichcanbedividedintofertilization,cleavage,morula,blastocyst,gastrulaandStagesoforganformation.Inaddition,duringtheembryonicdevelopmentofvertebrates,thecommonfeaturesofvariousanimalswillappearfirst(suchasskin),andthenspecializedstructures(suchasfishscales)willgraduallydevelop,andthereisadifferencebetweenmorecomplexspeciesandmoreprimitivespecies.Itwasquitesimilaratthebeginning,andthengraduallyincreasedthevariationwiththedevelopmenttime.
Oplodnění
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.
Výstřih
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.
· Kompletní štěpení
Radiální (mořští ježci, obojživelníci)
Bilaterální (ocasy, obojživelníci))
Spirála (annelids, měkkýši)
rotační (savci)
· Neúplné štěpení
p>Diskoidní (ryby, ptáci, plazi)
povrchní (hmyz)
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.
Organformace
Theprocessofformingvarioustissuesandorgansfromectoderm,mesodermandendodermiscalledorganogenesis,alsoknownasorganogenesis.Takethefrogembryoasanexample.Intheearlystageoforganformation,theectodermwillsaginwardaftertheprotrusion,forminganeuralridgeandaneuraltube;themesodermwillformasomiteandaspine,andthespacesurroundedbymesodermalsegmentsiscalledForthebodycavity.
Člověk EmbryoProcess
Člověkdevelopmentisgenerallylessthan8weeksforembryos,andmorethan8weeksforembryos.
1 měsíc
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 měsíce
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 měsíce
Thefetusgrowsarmsfirst,andthenlegs.Theheadandtailarebenttogether.Theheadhasears,nostrilsandchin.Theheadisaboutthelengthofthebody.1/3.Ovalhandsandfeetappearinthe11thweek,andfivedeeplineswillformfingers(toes).Twoeyesgrowonbothsidesofthehead,lipsandgumsappear,andthetaildisappears.Intheearlystageofembryonicdevelopment,thefetusdevelopsrapidly,andtheprimordiaofallorganshavebasicallybeenformedinthesecondandthirdmonths.Afterthat,onlyinternalcellsproliferatetoincreasetheirvolume.
4 měsíce
Fetalsexorgansappear,theeyesareturnedtothefrontoftheface,theforeheadisprominent,thenostrilsareopen,theearsarevisible,thelimbsbecomelonger,thefingersareidentifiableandtherearefingers(nail.Theheadandneckcanbeturnedandthemouthwillswallowamnioticfluid.
5 měsíců
Thefetusisabout25cmlong,weighs250g,andtheheadaccountsfor1/4ofthebodylength.Lanugohairandhairappearontheskin,sebaceousglandsandsweatglandsappear;therearefetusesintheintestinesFecesaccumulate,mainlybiledischargedfromthegallbladder.Thekidneyscanurinate,theurineisdischargedintotheamnioticfluid,andthefetus'slimbscanmove.
6 měsíců
Thefetusisabout30cmlongandweighs600-750g.Thefetusisrecognizable,thelungsbegintodevelop,thehairincreases,andtherearefatandwrinklesundertheskin.Thefetalheartrateis120-160beatsperminuteandcanbeheardwithanordinarystethoscope.Thefetuscanhearsounds,suchascarhornsandparentalconversations.
7 měsíců
Thefetusis35cmlongandweighs1,000-1,200g.Thebrainhasasulcusandcorticalstructure.However,thenumberandvolumeofbraincellshaveyettoincrease,nervefibersarenotlongenough,bonesandmusclesaredeveloping,andtheskull,spine,ribs,andlimbbonescanbeseenunderX-rays,becauseatthistimeboneshavebeguntocalcifyandjointsareclearlyvisible.Thefunctionofinternalorgansisgraduallyimproved,andhecanbreatheandcry.Theskinisredwithmanywrinkles,becausethereistoolittlesubcutaneousfat,itisdifficulttomaintainbodytemperatureifbornatthistime.
8 měsíců
Becausethemuscleshavebeendeveloped,andtheinterconnectionbetweenthenervecentersmakesthefetalmovementaqualitativechange.Atthistime,itwillnotonlypunchandkick,butalsoturnleftandrightormakea180or360degreeturn,whichwillwakeupthemotherfromthedream.Theeyesofthefetuscanbeopened,andthesurfaceoftheeyeballsisprotectedbyafilm.
9 měsíců
Plod má délku 45–47 cm a váží 2 000–2 300 g. Míra přežití plodů narozených v tomto měsíci může být až 95 %. Podkožní tuk se zvětšuje, vrásky postupně mizí, pleť je bledá a vlasy mizí.
10 měsíců
Plod je asi 50 cm dlouhý, váží asi 3 000 g, je bohatý na podkožní tuk a je chráněn mazoměsíčním hřbetem a klouby. Vlasy jsou silné, rovné a lesklé, nehty (prsty) přesahují přes konce prstů (u nohou) a chodidla na nohou mají více otisků dlaní.
Průlom
InApril2016,mycountryrealizedthedevelopmentofmammalianembryosinspaceforthefirsttime,andthiswasthefirsttimeintheworldthatmammalianembryosdevelopedinspace.