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The Biology of Prenatal Development




IBHAYOLOGI LEPHATSELENE NEKUKHULA KWEMNTFWANA LOSESESIBELETFWENI SENINA

.Siswati [Swati (siSwati)]


 
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Chapter 1   Introduction

Inchubo le ngayo izayigothi leyinhlayiya yinye yemuntfu iba ngumuntfu lomdzala lotinhlayiya letilikhulu lemathriliyoni etinhlayiya mhlawumbe sehlakalo lesibabateka kunato tonkhe kuyo yonkhe imvelo.

Kungunyalo bacwaningi bayati kutsi leminyenti yemisebenti leyetayelekile leyentiwa ngumtimba wemuntfu lomdzala icalisa ngekuhamba kwesikhatsi sekutetfwala esikhatsini lesinyenti lokwenteka emuva le umuntfu angakatalwa.

Sigaba sekukhula ngembikwekutsi umuntfu atalwe siya ngekuya sicondisiswa njengesikhatsi sekwenta emalungiselelo le ngaso umuntfu lowakhekako atfola ngaso takhiwo letinyenti, futsi etayela kwenta tintfo letinyenti nemakhono lamanyenti, lokundzingakalela kutsi umuntfu akwati kuphila ngemuva kwekutsi asatelwe.

Chapter 2   Terminology

Ngalokwetayelekile kutetfwala emntfwini kutsatsa cishe emaviki la-38 nakubalwa kusukela esikhatsini sekukwakheka kwembewu, kumbe sekubamba sisu,kufike esikhatsini sekutalwa kwemntfwana.

Ngekuhamba kwesikhatsi lesingemaviki la-8 ekucala ngemuva kwekwakheka kwembewu yemuntfu, umuntfu lowakhekako ubitwa ngekutsi yi-embriyo, lokusho kutsi "yakhekako ngekhatsi." Lesikhatsi lesi, lesibitwa ngekutsi sikhatsi sekuba yi-embriyo, sikhatsi lapho kwakheka ngaso letinyenti tetinhlelo temtimba.

Kusukela ekupheleni kwemaviki la-8 kuze kube sekugcineni kwekutetfwala, "lomuntfu lowakhekako ubitwa ngekutsi yifithasi," lokusho kutsi "umnftwana losengakatalwa." Ngalesikhatsi lesi,lesibitwa ngekutsi sikhatsi sekuba yifithasi, umtimba uyakhula ube mkhudlwana futsi tinhlelo tawo ticalisa kusebenta.

Tonkhe tigaba tekuba yi-embriyo nekuba yifithasi kuloluhlelo lolu ticondzise esikhatsinilesisukela ekwakhekeni kwembewu yemuntfu.

The Embryonic Period (The First 8 Weeks)

Embryonic Development: The First 4 Weeks

Chapter 3   Fertilization

Nawukhuluma ngekwebhayologi, "kwakheka kwemuntfu kucalisa ngekwakheka kwembewu," ngalesikhatsi indvodza nemfati bahlanganisa 23 ngamunye wemakhromozomu abo lokwenteka ngekuhlangana kwetinhlayiya tabo tekutala.

Inhlayiya yemfati yekutala ibitwa ngalokwetayelekile ngekutsi "licandza" kepha ligama lakhona lelifanele yi-usayithi.

Ngalokufanako, inhlayiya yendvodza yekutala yatiwa ngalokwetayelekile ngekutsi "budvodza" kepha ligama lelinconotekako lakhona yispemathozoni.

Ngemuva kwekutsi sekuphume i-usayithi esibeletfweni semfati lokwenteka ngendlela lebitwa ngekutsi kuphuma kwelicandza, i-usiyothi kanye nespemathozoni kuyahlangana ngekhatsi etfunjini linye lematfumbu esibeletfo, lekuvamise kubhekiswa kuwo njengemaFalophiyeni shubhu.

Ematfumbu esibeletfo achumanisa sibeletfo semfati neyutherasi kumbe sibeletfo.

I-emrbiyo lenenhlayiya yinye ledaleka lapho ibitwa ngekutsi yizayigothi, lokusho kutsi "lokuboshelwe kumbe lokuhlanganiswe ndzawonye."

Chapter 4   DNA, Cell Division, and Early Pregnancy Factor (EPF)

Emakhromozomu la-46 ezayigothi amelele sigaba sekucala lesingakavami sesitfombe semfanekiso lophelele weluhlelo lwelufuto lwemuntfu lomusha. Loluhlelo lolukhulu lolu luhlala ngekhatsi etinhlayiyaneni letisongekile tacina letibitwa ngekutsi yi-DNA. Ticuketse telayeto letimayelana nekwakheka kwawo wonke umtimba.

Tinhlayiyana te-DNA tifana nesitebhisi lesishwilekile lesatiwa ngekutsi yi-double helix. Letenyuko talesitebhisi tentiwe ngetinhlayiyana letihamba ngatimbili, kumbe emabheyisi, labitwa ngekutsi yigwanayni, sayithosin, adenayni, ne-thaymin.

Igwanayni ihambisana ngakubili nesayithosin kuphela, kutsi i-adenayni yona ihambisane nethaymin. Leyo naleyo inhlayiya yemuntfu Icuketse cishe 3 wetigidzi tetigidzi talamabheyisi lahamba ngamabili.

I-DNA yenhlayiya yinye icuketse lwati lolunyenti kangangekutsi kube bekulwati lolubhalwe ngemagama, kubhala nje kuphela luhlu lweluhlavu lwekucala lwaleyo naleyo bheyisi bekutawudzinga ngetulu kwemakhasi lasigidzi netinkhulungawane letingemakhulu lasihlanu embhalo!

Nakube beyingandlalwa phansi ilandzelane, i-DNA lesenhlayiyeni yemuntfu yinye beyingalingana na-3 1/3 wemafidi kumbe 1 mitha.

Kube besingayelula yonkhe i-DNA lengekhatsi kwetinhlayiya letisemntfwini lomdzala letilikhulu lemathriliyoni, beyingaba libanga lelingetulu kwemamayela langemashumi lasitfupha nakutsatfu wemabhiliyoni. Leli libanga lelingangekusuka emhlabeni uye elangeni uphindze ubuye tikhatsi leti-340.

Cishe 24 kuye ku-30 wema-awa ngemuva kwekwakheka kwembewu yemuntfu, izayigothi iyacedza kwehlukaniseka kwekucala kwenhlayiya yayo. Ngendlela yechubo yemayithosis, inhlayiya yinye ichekeka ibe tinhlayiya timbili,timbili tichekeke tibe tine, njalonjalo.

Emuva le kusaphele 24 kuya ku 48 wema-awa kucalise kwakheka kwembewu yemuntfu, kungacinisekiswa kwekutsi umuntfu utetfwele ngekutsi kutfolakale ihomoni lebitwa ngekutsi "luphawu lwekucalisa kutetfwala" engatini yenina.

Chapter 5   Early Stages (Morula and Blastocyst) and Stem Cells

Ngemuva kwa-3 kuya ku-4 wemalanga kwakheke imbewu yemuntfu, tinhlayiya letichekeka emkhatsini te-embriyo tiba yindzingilita bese kutsi i-embriyo ibitwa ngekutsi yimorula.

Emalangeni la-4 kuya ku-5, kwakheka imbobo ngekhatsi kwendzingilita yetinhlayiya bese kutsi i-embriyo seyibitwa ngekutsi yiblastosist.

Tinhlayiya letingekhatsi kweblastosist tibitwa ngekutsi ngumhlambi wetinhlayiya tangekhatsi futsi ngito letakha inhloko, umtimba,kanye naletinye takhiwo letibalulekile emntfwini lowakhekako.

Tinhlayiya letingekhatsi kwemhlambi wetinhlayiya tangekhatsi tibitwa ngekutsi tinhlayiyasicu te-embriyo ngobe tiyakwati kwakha leyo naleyo yaletinhlobo tetinhlayiya letingetulu kwa-200 leticuketfwe ngumtimba wemuntfu.

Chapter 6   1 to 1½ Weeks: Implantation and Human Chorionic Gonadotropin (hCG)

Ngemuva kwekuhamba yehle ngelitfumbu lesibeletfo, i-embriyo leseyincane itinamatselisa emtsangaleni wangekhatsi wesibeletfo senina. Lenchubo lena, lebitwa ngekutsi kumila, icalisa ngemuva kwa-6 wemalanga ibuye iphele ngemuva kwa-10 kuya ku-12 wemalanga yakhekile imbewu yemuntfu.

Tinhlayiya te-embriyo lekhulako ticalisa kukhipha ihomoni lebitwa ngekutsi yikhoriyonikhi gonadothrophini yemuntfu,kumbe i-hCG, lekuyintfo leba khona kuletinyenti tinhlobo tekuhlola kutsi umuntfu utetfwele yini.

I-HCG itjela emahomoni latfolakala ebafatini kutsi atsikamete luhlelo wekuya esikhatsini tinyanga tonkhe ngalokwetayelekile, kuze kutetfwala kuchubeke.

Chapter 7   The Placenta and Umbilical Cord

Ngemuva kwekumila, tinhlayiya letile emaphetselweni eblastosisti tihlumisa incenye yesakhiwo lesibitwa ngekutsi yiplasentha, lekungiyo leba ngumchumanisi emkhatsini wetinhlelo temitsambo yengati tenina nete-embriyo.

Iplasentha iletsela umuntfu Lowakhekako i-oksijini, kudla, emahomoni, kanye nemutsi lokusuka kunina; ikhiphe konkhe lokulahliwe; futsi ivimbele kutsi ingati yenina ingahlangani nengati ye-embriyo nefithasi.

Iplasentha iphindze ikhicite emahomoni futsi igcine lizinga lekushisa kwemtimba we-embriyo nefithasi lisetudlwana kancane kunelenina.

Iplasentha ichumana nemuntfu lowakhekako ngemitsambo yenkhaba.

Emandla eplasenta ekuniketa Imphilo angafaniswa nemandla eligumbi lalabagula kakhulu lelitfolakala etibhedlela tesimanjealamuhla.

Chapter 8   Nutrition and Protection

Evikini le-1, tinhlayiya tencumbi yetinhlayiya letingekhatsi takha tincwencwe timbili letibitwa ngekutsi yihayiphoblast kanye ne-ephiblast.

Ihayiphoblast yenta kutsi kumile sikhwama semtfubi welicandza, lekungilesinye setakhiwo lesenta kutsi unina akwati kuniketa i-embriyo leseyincane kudla

Tinhlayiya letiku-ephiblast takha inyama letsambile lebitwa ngekutsi yi-amniyoni, lapho i-embriyo, ngekuhamba kwesikhatsi kulandzele ifithasi, kutawukhulela khona aze umntfwana atalwe.

Chapter 9   2 to 4 Weeks: Germ Layers and Organ Formation

Ngesikhatsi cishe lesingu 2 1/2 wemaviki, i-ephiblast ibe seyakhe 3 weticubu letikhetsekile, kumbe tingogo tetimbewana, letibitwa ngekutsi yi-ekthodem, i-endodem, kanye nemesodem.

I-ectodem yenta kutsi kumile takhiwo letinyentana kufake ekhatsi ingcondvo, umgogodla, imiva, sikhumba, tingalo, kanye netinwele.

I-endodem ikhicita lucwecwe loluvalewendlalele umgudvu wekuphefumula kanye nemgudvu logaya kudla, futsi imilisa tincenye tetakhiwo letinkhulu temtimba letifana nesibindzi kanye nemalulu.

Imesodem yakha inhlitiyo, tinso, ematsambo, ikhathilegi, imisipha, tinhlayiya tengati, kanye naletinye takhiwo.

Emavikini la-3 ingcondvo iyehlukaniseka iba tigaba leti-3 letinkhulu letibitwa ngekutsi yingcondvo lesembili, ingcondvo lesemkhatsini, kanye nengcondvo lesemuva.

Kukhula kweluhlelo lwekuphefumula kanye neluhlelo lwekugaya kudla nako sekucalile.

Ngalesikhatsi tinhlayiya tengati tekucala tivela esikhwameni semtfubi welicandza, kwakheka imitsambno yengati kuyo yonkhe i-embriyo, futsi kucalisa nekubonakala inhlitiyo lemisiphasipha.

Masinyane emvakwaloko, inhlitiyo lekhula masinyane iyatisonga ivaleke ibe ngemagumbi lehlukene icalise kwakheka.

Inhlitiyo icalisa kushaya emavikini la-3 nelilanga linye ngemuva kwekwakheka kwembewu yemuntfu.

Luhlelo lwekuhamba kwengati luhlelo lwekucala lwemtimba, kumbe licembu letitfo temtimba letihambisanako, lolucalisa kusebenta.

Chapter 10   3 to 4 Weeks: The Folding of the Embryo

Emkhatsini wemaviki la-3 nala-4, luhlelo lwemtimba lucalisa kubonakala ngalesikhatsi ingcondvo, umgogodla, kanye nenhlitiyo ye-embriyo sekubonakala kalula eceleni kwesikhwama semtfubi welicandza.

Lokukhula masinyane kubangela kutsi i-embryo lekungashiyo kutsi isicabati ivaleke. Lenchubo lena ifaka incenye yesikhwama semtfubi welicandza ngekhatsi elucwecweni lwemgudvu logaya kudla bese kwakheka sifuba kanye nendzawo yesisu kwalomuntfu lowakhekako.

Embryonic Development: 4 to 6 Weeks

Chapter 11   4 Weeks: Amniotic Fluid

Emavikini la-4 i-amniyoni lekhanya ngale igocotela i-embriyo esikhwameni lesigcwele lokusamantana. Lolokusamantana lokuvikelekile emagciwaneni, lokubitwa ngekutsi ngemantana e-amniyoni, kuvikela i-embriyo kutsi ingalimali.

Chapter 12   The Heart in Action

Njengalokulindzelekile, inhlitiyo ishaya cishe 113 wetikhatsi ngeliminithi.

Nyalo caphela kutsi inhlitiyo intjintja umbala ngalesikhatsi ingati ingena ibuye iphume emagunjini ayo leso naleso sikhatsi ishaya.

Inhlitiyo itawushaya cishe tikhatsi let-54 wetigidzi ngembikwekutsi umntfwana atalwe futsi itawushaya ngetulu kwetikhatsi leti-3.2 wetigidzi tetigidzi ngekuhamba kwesikhatsi sekuphila lesiminyaka le-80.

Chapter 13   Brain Growth

Kukhula masinyane kwengcondvo Kubonakala ngekugucuka kwesimo sengcondvo lesembili, ingcondvo lesemkhatsini kanye nengcondvo lesemuva.

Chapter 14   Limb Buds

Ticubu tangenhla kanye neticubu Tangentasi ticalisa kukhula ngalesikhatsi kuvumbuka tigadlana teticubu emavikini la-4.

Ngalesikhatsi lesi sikhumba sibonakalisa ngale ngobe siyinhlayiya yinye kuphela ngebukhulu.

Ngalesikhatsi sikhumba siya ngekukhula, angeke sisabonakala ngale, lokusho kutsi sitawukhona kubona kukhula kwetitfo temtimba tangekhatsi lokungenani lenye inyanga kuphela.


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