Ekupheleni kweiveki ezi-4 iziqhamo zakhula zibe yi-1 mm kwaye ubukhulu bayo bufana nembewu yepoppy. Kule nqanaba lokuphuhliswa, iqanda elisuka kwiqanda lomntwana liqala ukuguqula libe ngumbungu. Xa ukhulelwe kwisithuba seveki ubuninzi besiqhamo nakuba kunjalo, kodwa umbungu uvakalelwa ngokuzithemba ngakumbi kwaye ngokunyanisekileyo uqhotyoshelwe eludongeni lwesisu.
Ukuqala ngeli xesha, inethiwekhi ye-vascular ikhiqizwa kwindawo apho umbungu uphahla khona eludongeni lwe-uterine. Ezi zihlunu zidibanisa umntwana osasa kunye nonina, kwaye ngezo zinto akazukufumana konke okufunekayo ukuze kubekho ubomi kunye nophuhliso. Xa ubudala be-fetus iiveki ezi-4, i-embrayo iqalisa ukuvelisa izitho zange-germ, ukubonelela ngesondlo, ukuphefumula nokukhusela. Mabhunga afaka:
- Ikhetho . I membrane yangaphandle ye-embryonic ekhuthaza ukudala i-placenta, eyenziwe ngokupheleleyo ekupheleni kweveki yeshumi elinesibini.
- Amnion . I-cavity, eyi-fetal bladder, eyenza i-amniotic fluid, apho i-embryo ikhona.
- I-yolk sac . Uneminyaka engama-7 ukuya kwe-8, uxanduva lwe-hematopoiesis yesibindi.
Umntwana ubonakala njani kwiiveki ezi-4?
Abantu abaninzi bayazibuza ukuba umntwana sele eveki ezine. Ngeli xesha, libukeka njengediski equlethwe ngamatye amathathu eselintshi - izigcawu zentsholongwane:
- i-ectoderm (ungqimba lwangaphandle), olujongene nokubunjwa kwesikhumba, iinwele, inkqubo ye-nervous, i-lens kunye ne-tooth eamel;
- I-Endoderm (umgca wangaphakathi), uxanduva lokuseka inkqubo yokutya, isibindi, i-thyroid kunye ne-pancreas;
- i-mesoderm (uluhlu oluphakathi), ekugqibeleni luya kuba ngamathambo, izicubu ezinokuxhamla kunye nemisipha, igazi kunye neenkqubo ezixhamlayo, izitho zomzimba.
Ukukhulelwa kuya kubonakala kuphela ekupheleni kweveki, ukuba kwenziwe uhlalutyo lwe-hCG. Ngokumalunga nokuhlolwa kwekhaya, akahlali ekwazi ukuqonda ixesha elinjalo, ngenxa yokuba umchamo wesifazane uqulethe i-hormone enganeleyo.