Final answer:
The trophoblast is the fetal tissue that contributes to the formation of the placenta, particularly through its differentiation into chorionic villi that interface with maternal tissues to facilitate nutrient and waste exchange.
Step-by-step explanation:
The formation of the placenta involves tissues from both the mother and the developing fetus. The fetal tissue that contributes to the formation of the placenta is known as the trophoblast. This layer of cells initially surrounds the blastocyst and eventually gives rise to the chorionic villi, which penetrates the maternal endometrium to form the fetal portion of the placenta.
The trophoblast differentiates into two layers: the syncytiotrophoblast and the cytotrophoblast. These layers proliferate along with a layer of extraembryonic mesoderm cells, forming the chorionic membrane or chorion. The chorionic villi extend from this membrane and become immersed in the endometrium, allowing for the exchange of nutrients, oxygen, and waste between the maternal and fetal blood vessels.
The placenta is critically important for the exchange of substances between the mother and fetus without blood mixing. It is also permeable to certain substances, which emphasizes the need for avoiding fetotoxic substances during pregnancy to prevent adverse effects such as fetal alcohol spectrum disorders (FASD).