Ngaphambi kweviki lesishiyagalombili lokukhulelwa, i-embryo iqala, izitho zayo zibekwe, futhi emva kwalesi sikhathi umbungu unamalungu amakhulu, bese kuphela ukuthuthukiswa kwawo kwenzeka. Isikhathi sokufika emavikini ayisishiyagalombili sibizwa ngokuthi i-embryonic, futhi emva kwamasonto ayisishiyagalombili ayisisona umbungu, kepha i-fetus, ne-fetal period iqala.
Izindlela zokuqala zokuthuthukiswa kombungu womuntu
Izindlela zokuqala zokuthuthukiswa kombungu zingalandelwa ngosuku. Ngosuku lokuqala iqanda elithombeni elihlangene lihlangana nensimu nesigaba sokuqala - ukukhulelwa kwenzeka. Ngosuku olulandelayo isigaba se-zygote siqala - iseli esinama-nuclei amabili emgodleni walo ngamaqoqo angama-haproid ama-chromosomes, ngemuva kokuhlanganiswa kwe-cell ne-nucleus eyodwa nesethi ye-chromosome ye-diploid.
Ngolunye usuku emva kwalokhu, iseli liqala ukuhlukanisa - isigaba se-morula noma ukuchotshoza kuqala, kuthatha izinsuku ezingu-4. Iseli ngayinye lihlukaniswe kuze kube yilapho ibhola elingqimba lamangqamuzana elinomgudu ngaphakathi kwe-blastula lenziwa. Kusuka kumaseli alo esikhathini esizayo esakhiwe i-trophoblast (i-placenta yesikhathi esizayo) ne-embryoblast (ingane ezayo).
Ngosuku lwesishiyagalombili i-blastula ingena emgodleni wesibindi, lapho iqala ukufihla khona ama-enzyme okudingekayo ukuqala kwesigaba esilandelayo - ukufakelwa kwe-embryo , okuphela kwezinsuku ezingu-2.
Embryo emva kokufakelwa
Ukufakwa kwesisu nje kudala esigabeni esilandelayo sokuthuthukiswa kombungu - gastrula. Ibhola elilodwa eliyingqimba lama-embryoblast amangqamuzana liphenduka ibhola elingaphansi. Ingqimba yangaphandle yama-embryon ibizwa nge-ectoderm futhi iphakamisa i-epithelium yesikhumba kanye nezitho zesimiso sezinzwa. Lesi yisigaba sokuhlukaniswa kwamashidi okumbumbulu.
Ukusuka ungqimba lwangaphandle (endoderm) esikhathini esizayo, zonke izembozo ze-epithelial zezingaphakathi zangaphakathi ze-fetus (isisu, intathu, i-bronchi namaphaphu), kanye nesibindi namaphakhesi. Lezi zigaba ezimbili zigoba, zakha ama-bubbles (i-amniotic - i-amniotic i-fluid kanye ne-yolk ezayo esizayo) kuqala ukupha umbungu, bese uyisitho se-hemopoietic).
Kusukela kulo mzuzu (ophela ekuqaleni kweviki lesi-3 lokukhulelwa), isigaba sokugcina sokuthuthukiswa kwe-embryo - organogenesis - siqala.
Ngokushesha ngaphambi kwalokhu, i-embryo ijika, i-ectoderm yayo ihlanganisa umbungu kusuka ngaphandle,
Ngemuva kwamasonto amane, izitho zangaphakathi ze-fetus ziqala ukufakwa. Ngeviki le-6, ama-rudiments wezitho zomzimba azovela, kuze kube sekupheleni kwe-7, inhliziyo kanye namakamelo ayo akhiwe, kuze kube yilapho kuhlanganiswa zonke izitho zangaphakathi, amaphaphu, nezitho zangasese. Ngeviki 9, zonke izitho kanye nezinhlelo zakhiwa ngokuphelele, bese kuphela ukuhlukaniswa kwabo kuzokwenzeka.