The list below describes (in no particular order) someearly events of the pre-embryonic period.
1 – Cortical reaction
2 – Blastocoel forms
3 – Yolk sac and amnion start to form
4 – Dichorionic-Diamnionic twins
5 – Four celled pre-embryo
6 – Human chorionic gonadotropin present in urine
The 6 steps above are not in the correctorder.
