Final answer:
Chorion Frondosum refers to the part of the chorion that combines with maternal tissue to form the fetal portion of the placenta. It is located at the external fetal membrane that lies beside the uterine wall. The key feature of the chorion is the chorionic villi, which help establish the connection with the maternal blood supply.
Step-by-step explanation:
The Chorion Frondosum is the portion of the chorion that, along with the decidua basalis, forms the fetal side of the placenta. The chorion is a membrane that develops from the syncytiotrophoblast, cytotrophoblast, and mesoderm and surrounds the embryo, ultimately playing a pivotal role in the formation of the placenta through the chorionic villi. These villi are projections of the chorionic membrane that infiltrate the endometrium, the inner lining of the uterus, where they establish the exchange of nutrients and waste between the mother and the developing fetus.
The chorion is one of the extra-embryonic membranes and the last one that envelops all others, including the amnion, which is another protective membrane that contains the amniotic fluid, surrounds, and protects the embryo. The chorionic villi are essential for the establishment of the fetal blood supply and are formed as a result of the rapid proliferation of chorionic material.