CLEAVAGE zona pellucida 2 cell stage 4 cell stage MORULA 批S 8 cell stage por nuceus (n) oviduct EARLY BLASTOCYST ②FERTILISATION inner cell mass LATE BLASTOCYST follicular cell secondary oocyte ovary ①OVULATION blastocoel cavity trophoblast 排卵、受精与卵裂过程 排卵、受精与卵裂过程