cleavage of the zygote
da 1 = 2 cells +polar body
day 2 = 4 cells+ blastomere
day 2 and 1/2= 9 cells
day 3= 16-cells: morula(latin mulberry)
day4= 58 cells blastocyst
day 5 = balstocyst with zona pelucida trophoblast, inner cell mass, blastocoele