The egg from the ovary is surrounded by a few layers of follicle cells

The enzyme disperses the follicles and breaks down some of the egg membrane

Only 1 sperm nucleus enters the cell and fuses with the nucleus to form a zygote

As soon as a sperm enters the egg, the cell membrane changes so that no further entry will occur

Cilia lining in the oviduct and peristaltic movement help move the zygote to the uterus

Eventually, the embryo becomes embedded in the uterine lining

Villi will start to grow from the embryo into the uterine lining. They contain the blood capillaries of the embryo

The villi and the uterine lining in which the villi is embedded is called the placenta

The amniotic sac begins to develop at about the same time as the placenta

The amniotic sac encloses the embryo in a fluid-filled space called the amniotic sac, which contains amniotic fluid