Which structure develops from the outer layer of the blastocyst during implantation?

During the process of implantation, the outer layer of the blastocyst, known as the trophoblast, differentiates and gives rise to the chorion. The chorion plays a critical role in the early stages of pregnancy as it contributes to the formation of the placenta, which facilitates nutrient and gas exchange between the mother and the developing embryo.

The embryo itself develops from the inner cell mass of the blastocyst, not the outer layer. The amnion and allantois are additional structures associated with the developing embryo but originate from different cell types and functions. The amnion forms a protective membrane around the embryo, while the allantois is involved in waste management and eventually contributes to the umbilical cord. Therefore, the chorion is the correct answer as it specifically develops from the outer layer during the implantation phase.