Placenta. Light micrograph of a section through placental tissue, showing chorionic villi with blood vessels (red) and connective tissue (blue). The placenta is the temporary organ that connects a developing foetus to its mother. The chorionic villi are projections of foetal tissue into the maternal part of the placenta. The many blood vessels in the villi allow foetal blood to come in close contact with the mother's blood. They enable the exchange of gases, nutrients and waste with the mother's blood since the foetus cannot breathe, feed or excrete while in the womb.