|Source: Centro Riproduzione Assistita, Catania, Italy.|
Note:Once the morula develops an inner cavity, the embryo has achieved a new developmental milestone and is called a blastocyst.
Note: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
3. early blastocyst cavity
4. inner cell mass
|All ages referenced to fertilization, not last menstrual period.|