The chorion is one of the important fetal membranes that is formed during embryonic development in mammals. It encases the embryo and fetus together with the amnion, providing protection and support. The chorion produces chorionic villi, which are finger-like projections that develop into the placenta. These villi play a crucial role in facilitating nutrient and waste exchange between the maternal and fetal circulatory systems, ensuring the transfer of essential substances such as oxygen, nutrients, and waste products. Additionally, the chorion secretes hormones that help maintain the pregnancy and prevent the mother's immune system from rejecting the developing fetus. Thus, the chorion is a critical component of the complex system that sustains and nourishes the growing fetus throughout pregnancy.