Mucous structure changes 2 days a month Only strongest sperm can penetrate. Mucous cleans bacteria off sperm.
Female orgasm helps sperm thru plug.
Only 100 sperm reach ovum. Enzymes from sperm s acrosome digest their way through the zona pellucida. Change in zona pellucida prevents entry of more than one sperm. Blastula implants in uterine lining. Three developmental processes Cleavage Gastrulation Induction Cleavage Zygote divides repeatedly to produce a blastula, a hollow ball of cells.