Final answer:
The organ responsible for the exchange of nutrients, oxygen, and waste products between a mother and a fetus is the placenta. It connects through the umbilical cord and facilitates the transfer of essential substances while protecting the fetus from the maternal immune system.
Step-by-step explanation:
The organ that allows nutrients, oxygen, and waste products to be exchanged between a mother and fetus is the placenta. The placenta is a temporary but critical organ in placental mammals like humans, establishing a connection between the developing embryo or fetus and the mother. It functions as a conduit for the transfer of nutrients, oxygen, antibodies, hormones, and other essential substances. Through this interface, it also enables the removal of fetal waste such as urea and carbon dioxide. The fetus is connected to the placenta via the umbilical cord, which comprises one umbilical vein and two umbilical arteries. These vessels are responsible for the flow of oxygen-rich blood from the mother to the fetus, and vice versa for the oxygen-depleted blood laden with wastes.
The exchange of substances between the fetus and the mother takes place without direct mixing of their bloodstreams, facilitated by a sponge-like structure formed by membranes and blood vessels of both the mother and the embryo. This arrangement safeguards the fetus against the mother's immune system, which might otherwise recognize it as a foreign body. Substances like glucose and amino acids are transferred via facilitated diffusion and active transport, respectively, to meet the high demand of the developing fetus.