Following are the events which occur after fertilization and formation of Zygote.
- Zygote moves through oviduct and cleavage begins,forms blastomeres.
- At 8-16 cell stage embryo is called morula.Mitosis continues and embryo moves to uterus. The blastomeres form outer layer called trophoblast andthe rest of the cells form mass of cells called as Inner cell mass(ICM). This stage is called as blastocyst.
- At blastocyst stage embryo gets implanted into uterus wall.
- After implantation of the embryo, placenta starts developing in the human female. The chorionic villi from the embryo and uterine tissue, become interdigitated with each other and jointly form a structural and functional unit between developing embryo(foetus) and maternal body called placenta.
- Placenta acts as an endocrine tissue and produces several hormones like human chorionicgonadotropin (hCG), human placental lactogen(hPL), estrogen, placental progestogensin the maternal blood.
- Increased level of these hormones is essential for supporting the foetal growth/metabolic changes in mother and maintenance of pregnancy
