Once the morula develops an inner cavity, the embryo has achieved a new developmental milestone and is called a blastocyst.
The cells lining the perimeter of the embryo will help form the placenta and are called trophoblast cells. These cells bring water, minerals, and amino acids from the nutrient-rich environment outside the embryo into the blastocyst cavity where they can reach the cells of the inner cell mass.
- 1. zona pellucida
- 2. trophoblast
- 3. early blastocyst cavity
- 4. inner cell mass