Chorion in primates forms the placenta. This chorionic placenta protects the embryo and allows metabolic exchange between the foetus and the mother. It facilitates the supply of oxygen and removal of CO2, waste material from the embryo. It acts as an endocrine gland and secretes hormones like human chorionic gonadotropin (HCG), human placental lactogen, progesterone and estrogen. The foetus is connected by the umbilical cord to the placenta. Through the blood vessels in the umbilical cord, the foetus receives all the necessary nutrition, oxygen, and life support from the mother through the placenta.