Are the embryonic sack and the placenta the same thing?

No, the embryonic sac and the placenta are not the same thing. The embryonic sac, or amniotic sac, is a fluid-filled structure that surrounds and protects the developing embryo. In contrast, the placenta is an organ that forms during pregnancy, providing nutrients and oxygen to the fetus and removing waste products. While both are crucial for fetal development, they serve different functions and structures.