Cleavage and implantation.

A Days 1-4 Cleavage. Mitotic divisions divide the zygote cytoplasm among an increasing number of cells. inner cell mass B Days 5—7 Blastooyst forms and expands then sheds its protein coat. endornetrial cavity inside epithelium the uterus C Days 8-9 Implantation starts. The blastocyst attaches to the uterine lining (the endometrium) and begins to sink into it. D Days 10-11 The inner cell mass now has two layers. One near the blastocoel will become the yolk sac. The other, the embryonic disk, will give rise to the embryo. actual size E Day 14 Projections from the chorion (chorionic villi) begin to grow into blood-filled spaces in the endornetrium. The amniotic cavity has filled with fluid. actual size