Final answer:
The placenta receives its circulation from the maternal blood supply through the interaction at the chorionic villi. Oxygenated blood is carried to the fetus through the umbilical vein, while deoxygenated blood and waste are carried back to the placenta via the umbilical arteries.
Step-by-step explanation:
The Source of Circulation for the Placenta
The placenta is a critical structure in fetal development, providing necessary oxygen and nutrients to the fetus. The main source of circulation for the placenta is the maternal blood supply. Maternal blood flows into the spaces between the chorionic villi, which are part of the placenta, allowing the exchange of substances between the fetal blood and the maternal blood. This exchange does not involve the mixing of the two blood supplies. Oxygenated blood is delivered to the fetus via the umbilical vein, and from there it travels to the fetus's inferior vena cava through the ductus venosus. Meanwhile, two umbilical arteries carry deoxygenated blood and waste from the fetus to the placenta.
Within the placenta, the exchange of gases and other substances occurs, facilitated by the unique environment in the placental villi, where maternal and fetal blood come into close proximity without direct mixing. Oxygen and nutrients pass from the mother's blood through the chorionic villi and enter the fetal bloodstream. The transfer of substances between mother and fetus is crucial for the growing embryo, and the placenta is perfectly adapted for this function with features like facilitated diffusion and active transport for certain nutrients.