Final answer:
Oxygenated blood returns to the heart through four pulmonary veins, with two originating from each lung, and they empty into the left atrium, completing the pulmonary circulation.
Step-by-step explanation:
The pulmonary circulation is a vital component of the circulatory system which involves the heart and the lungs, facilitating the exchange of gases by transporting oxygen-poor blood from the heart to the lungs, where it gets oxygenated, and then returning oxygen-rich blood to the heart. Specifically, oxygenated blood returns to the heart via four pulmonary veins, with two from the right lung and two from the left lung. These veins deliver oxygenated blood directly into the left atrium of the heart, thereby completing the pulmonary circuit.