Final answer:
The fetus receives oxygen-rich blood from the placenta through the umbilical vein and returns oxygen-depleted blood via the umbilical arteries.
Step-by-step explanation:
The fetus receives its blood from the placenta primarily through the umbilical vein. This vein carries oxygen-rich blood from the placenta directly to the fetal heart. After the exchange of gases and nutrients within the placenta, the oxygen-depleted fetal blood, including wastes and carbon dioxide, is then carried away from the fetus to the placenta via the umbilical arteries. These structures are part of the fetal circulatory system, which uniquely adapts for the fetus to receive oxygen and nutrients while bypassing organs like the lungs and liver that are not fully functional in utero.