What structure does the trophoblast layer develop into?

The trophoblast layer plays a critical role in early pregnancy development by giving rise to the fetal membranes and the placenta. Initially, after fertilization, the trophoblast is the outer cell layer surrounding the developing blastocyst and is essential for implantation into the uterine wall. Upon attachment to the endometrium, the trophoblast differentiates into two distinct layers: the cytotrophoblast and the syncytiotrophoblast.

The syncytiotrophoblast is particularly important because it invades the maternal tissue, facilitating nutrient exchange and establishing a connection between the developing fetus and the mother. This development is crucial for the formation of the placenta, which serves as the lifeline for the growing embryo, providing oxygen and nutrients while also removing waste products. Additionally, the trophoblast contributes to the formation of the amniotic sac and chorion, essential protective fetal membranes.

In contrast, the other options represent structures that do not originate from the trophoblast. The embryo develops from the inner cell mass of the blastocyst, the umbilical cord forms later from structures integrating into the placental system, and the yolk sac, while supporting early embryonic development, is not derived from the trophoblast but rather from the embryo itself. Thus,