Ziziphi izigaba ze-embryogenesis?
Ixesha lokubambela ukuphuhliswa kwabantu lithatha iinyanga ezi-2 - oku kude kangakanani iinkqubo zokuguqulwa kombungu ekufikeni komntwana. Njengomphumo wale nqubo, umzimba usekwe ngokusetyenzisweni olufanayo kunye nomzimba omdala.
Kwinqanaba lokuqala, i-zygote yenziwa. Yakhiwe ngenxa yefusion yeeseli zesini zesini neyesetyhini. Eli xesha lihlala lifutshane. Emva kokuba kufike isigaba sokuqhekeka.
Ngeli xesha, ukunyuka kwetyeli eninzi kwenzeka. Kule meko, iiseli ezenziwe ngokutyunjwa zazibizwa ngokuba yi-blastomer. Okokuqala uqokelelo oluncinci lweseli luyakheka, olufana ne-raberry e-raberry ehlobo lwangaphandle, kwaye lwabizwa ngokuba yi-morula. Ngokuqhekeka okuqhubekayo, inani lamaseli liyakhula kwaye i-morula ithatha uhlobo oluthile olubanzi, i-blastula.
Emva kokuchotshozwa, isigaba esilandelayo, isigaba sesithathu sexesha lokubambela ukuphuhliswa komzimba, kukunyusa. Ithatha ukuguqulwa kwebhokisi elilodwa-ungqimba kwi-two-layered one, i.e. ukuthetha nje - kukho kabini iigobolondo. Kule meko, i-gastrula ngokwayo iqukethe amaqabunga ama-embryonic, i-ecto- ne-endoderms. Ngexesha lokuziphendulela kwazo zonke izinto eziphilayo, inkqubo yokwenza i-gastrulation yaba nzima ngokubunjwa kwe-axial complex (i-neural tube, axial squke, musculature), ebeka kwicala lokutshitshisa embryo ukusuka kwiqabunga lesi-3 le-embryonic.
Ixesha lesine libandakanya ukuhlukaniswa kwezinto eziphambili zezitho kunye nezicubu kunye nokuphuhliswa kwazo. Ngalokhu, kukho ukuhlanganiswa okuqinisiweyo kweengxenye kwiqela elilodwa. Ngoko, ukusuka kwinqanaba langaphandle le-endoderm, ukubunjwa kwamathambo epithelial ekwenzeni umtya wendlela yokutya, kunye neengqungquthela zawo. Ukususela kumama-mesoderm - iimisipha, kunye ne-epithelium ye-genitourinary system, i-memoustic serous yengqondo. I-mesenchyme yakha i-conen, i-cartilaginous, i-bone tissue, i-vascular system.
Ukubekwa kwezitho ezisisiseko kunye neenkqubo zenzeke njani?
Emva kokubhala zonke izigaba zexesha lokubambela ukuphuhliswa, siza kuphinda sichaze ukuba yeyiphi iistim kunye nezitho zenziwa kwiiveki nganye. Ngaloo ndlela, inkqubo yokutyhoboza ngexesha lokwakhiwa kombungu wesintu ihlala malunga neentsuku eziyi-3-4. Ngeli xesha, lihamba malunga namatye agugu ukuya kwindawo. Ngenxa yenkqubo yokuchotshoza kwi-blastomeres ephezulu, i-shell, eyenza inxaxheba ekutyeni imbungu, i-trophoblast. Ezi blastomeres, ezifumaneka ngqo kwiziko, zenza i-embryoblast, apho i-future body of the embryo yenziwa khona.
Ekubeni kwiveki yesibini yokuqala kwenkqubo yokuphuhlisa, umbungu ubhaptizwa eludongeni lwesisu. Ngelo xesha, ukubunjwa kwezakhiwo ezifana ne-yolk kunye ne-amniotic vesicles ziyabonwa. Emva kokuba benze i-mesenchyme, i-amnion yenziwa. Oku kubaluleke kakhulu kwimbumba ekhuselekileyo eyenza isikhwama, esiza kugcwaliswa ngawo onke ama-amniotic fluid.
Ngeveki yesithathu yokuphuhliswa kwamanzi, i-dense bundu yamaseli ekhulayo ikhutshwa ukusuka emva. Isiqendu saso esibizwa ngokuba yintloko, ukuqina, senza i-nodule ephambili. Yilo lwakhiwo oluvelisa ukuveliswa kwezinto ezifana ne-neural tube.
Kwiiveki ezi-4 ngaphandle kweembrane ze-extraembryonic, i-embryo ihamba ngokwemigangatho eyimpembelelo ngenxa yokukhula okuphuculweyo, amaqumrhu ahlukeneyo omzimba we-fetal eyokwenziwa. Ukufana nale nto, isigaba sokuqala senkqubo ye-organogenesis kunye ne-histogenesis yenzeka.
Ngeveki yesi-5 yokukhulelwa, iingubo zeengalo nemilenze zinokuchazwa ngokucacileyo, kwaye ngeveki yesi-6 iinqununu zihlukaniswe zibe ngamacandelo amakhulu. Phantse ekupheleni kweiveki ezi-7 ekuqhutyweni kwe-US kunokwenzeka ukubona izixhobo zeminwe. Ngoko, ngeveki 8 (le yithuba elingakanani ixesha elibambileyo), iimbumba zeembumba zizaliswe.
Ukuze ukhangele iinjongo eziphambili zexesha lokuphuhlisa, masibe phantsi kwetafile apho ziboniswa khona.
