Izimpikiswano zokukhulelwe, ukukhulelwa kanye nentuthuko yayo ngaso sonke isikhathi izikhathi eziphezulu eziphezulu zezihloko zabesifazane. Futhi, ngokudabukisayo, ulwazi mayelana nezisekelo "zokuzalwa kokuphila okusha" ngokuvamile kuvunyelwe "inkambo ye-biology ne-pestle" efundelwe eminyakeni yesikole. Ake sizame ukubamba futhi sifunde isakhiwo somuntu oyedwa wabalingiswa bale nqubo - iqanda lesifazane.
Ekuzalweni kwentombazane e-ovary, i-endocrine gland enesizinda sayo se-hormonal, kunezinhlobo ze-gametes ezilinganiselwa ezigidini ezingu-7 - amaqanda (gametes), okuyilowo nalowo, okungukuthi, angaba yisisekelo sokuphila okusha ngemuva kokukhulelwa. Kodwa kancane kancane lapho uneminyaka yobudala, inani lamaqanda liba lincane: eminyakeni engama-20 selivele liyizinkulungwane ezingu-600, futhi emva kwe-60 alitholakali nhlobo. Isisindo esinamandla samaseli wesifazane sivumela owesifazane ukuba abe umama ngisho noma eyodwa noma ingxenye yesinye isisu isusiwe.
Ngakho-ke, iseli lamaqanda (i-egg cell, i-ovum) liyisisindo esikhulu kunazo zonke zomzimba womuntu, iseli lesikhumba sokuzala liyingqimba (elincane noma elinganayo) elivuthwa futhi "ligcinwe" kumapulisi ama-ovari. Iphelelwe impela futhi ngaphambi kokufinyelela esibelethweni yenza indlela engaba ngu-10 cm ubude phakathi kwe-villi yangaphakathi ye-oviduct phakathi nezinsuku ezingu-4-7. Ubukhulu beqanda buphindwe kabili ngaphezu kwesayizi se-sperm cell - i-germ cell yesilisa kanye nezikhathi eziningana-ubukhulu bamanye amangqamuzana emzimbeni. Ububanzi bayo buyingxenye ye-100-170 μm. I-gamete yezinsikazi ihloselwe ukudluliselwa ekusetshenzisweni kokukhiqizwa kwe-haploid iqoqo lama-chromosomes angu-23 (i-autosomal engu-22 yokudlulisa ulwazi oluzuzwa ngokwefa + isondo esisodwa i-X i-chromosome ephethe ubulili bomntwana ongakazalwa).
Libukeka kanjani iqanda?
Uhlelo lwesakhiwo seqanda elivuthiwe, elakhiwa emva kokuvuthwa kwe-ovulation - ukukhululwa kweqanda kusuka e-follicle kuya emgodini wesisu, kukhonjiswa ngezansi.
Ngokuvamile, iqanda linesakhiwo esifana namanye amangqamuzana omzimba: i-nucleus, i-cytoplasm, ukuvinjelwa kwekhanda le-plasma. I-nucleus yama-Haploid eneqoqo lama-chromosomes angenhla kuleli qanda liphakathi. I-cytoplasm inezinhlobo ezihlukahlukene ze-ribosomes, izakhi ze-endoplasmic reticulum futhi equkethe ama-enzyme adingekayo ekuphefumuleni kwamaseli e-mitochondrial. Ingxenyeni yangaphandle ye-cytoplasm iqukethe i-secretory (cortical) granules, ekhishwa lapho iqhamuka eqanda le-sperm, esebenza ngegobolondo layo, okuphumela ekushintsheni kwisakhiwo se-oocyte futhi kuvimbela ukungena kweminye i-spermatozoa. Ama-grains asebenzayo e-cortical azokhuthaza ukukhulelwa okuphumelelayo.
Amagobolondo weqanda nawo enza umsebenzi wokuzivikela kanye nomsebenzi wokuhlela ukudla kwawo. Ngaphandle, iqanda lizungezwe igobolondo elikhazimulayo, elimbozwe ungqimba lwezincane ezincane - yilokho okuthiwa i-follicular coat noma umqhele ogqamile.
Umzimba we-polar uyiselula encane ukuthi, kanye neqanda, lakhiwa ngenxa ye-meiosis - ukuhlukaniswa kwe-cell progenitor ngesikhathi sokuvuthwa kwayo. Kuye kwafakazelwa ngokwesayensi ukuthi okuqukethwe komzimba we-polar kungaba yisisekelo sokuthola izifo ze-genetic.
Ukudla komzimba ngaphambi kokusungulwa kwodonga lwamaqanda kwenziwa ngosizo lwe-yolk granules-egcwele amafutha, inani elincane lamaprotheni, amavithamini nama-microelements.
Ikhwalithi ye-egg cell ekhula, ukusebenza kwayo kungathonywa yizinto ezinjalo zethonya langaphandle njengendawo yeselula, ukubunjwa kwamakhemikhali kanye nokushisa kwemvelo yeqanda. Ngaphezu kwalokho, indlela yokusebenza kwe-intracellular inomthelela omkhulu ekwenzeni ukuvuthwa kwayo. "Ukuntula", hhayi amaqanda okuvuthisa ngokuvamile kubangelwa ukungabi nabantwana. Lokhu kungenzeka, isibonelo, uma umjikelezo wesimiso uhlala ezinsukwini ezingaphansi kwezinsuku ezingu-21, noma ngaphezulu kwezinsuku ezingu-35. Ngaphansi kwezimo ezinjalo, iseli leqanda "alivuthanga", noma selivele lingasebenzi. Uma kungabikho uketshezi, ama-ovari akhiqiza ama-follicles, lapho ama-ovules avuthiwe khona. Ngakho, ngaphandle kwamaqanda, lapho i-spermatozoa ingena, ukukhulelwa akukwenzeka.