Within the blastocyst, the outer shell of cells that will develop into the chorionic sac and fetal portion of the placenta is called the:

1. The blastocyst organizes into two distinct cell populations around a fluid-filled cavity called the blastocoel. 2. One population, the inner cell mass, is fated to become the embryo itself. 3. The other population forms the outer shell of the blastocyst. 4. This outer shell is called the trophoblast, which develops into the chorionic sac and fetal portion of the placenta. _Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 28 "Development and Inheritance", p.1325 §Pre-implantation Embryonic Development_