The chorion is a membrane that helps form the chorionic villi which is connected to the endometrium and gives rise to the placenta. The endometrium is the mucous membrane that lines the inner surface of the uterus. Approximately every 28 days the female drops an ovum(egg), if the ovum is fertilized by the male sperm, the female becomes pregnant. If the ovum is not fertilized, the inner lining is shed and the female has her menstrual period. The placenta is the structure in the uterus that provides nourishment to the developing fetus via the umbilical cord. The umbilical cord is highly vascular, containing 2 arteries and 1 vein. These blood vessels supply the fetus with nutrients(glucose, oxygen) and remove waste products(carbon dioxide).
The chorion is the outer membrane that encloses the embryo in reptiles, birds, and mammals. It is one of four fetal membranes which includes the allantois, amnion, chorion, and yolk sac. The function of the chorion is to contribute to the development of the placenta in placental mammals.
The main function of the placenta is to move oxygenated blood into the bloodstream of the developing baby and in turn, move carbon dioxide out. It also ensures that nutrients are received, and wastes are taken away. It also plays a very important role in hCG production and protects the baby from infection.