Final answer:
The pulmonary circuit involves the flow of deoxygenated blood from the right atrium, through the right ventricle to the lungs via the pulmonary arteries. There, oxygenation occurs and carbon dioxide is expelled, and then oxygen-rich blood returns to the left atrium via the pulmonary veins.
Step-by-step explanation:
Pulmonary Circuit
The pulmonary circuit is a crucial component of cardiovascular circulation, involving the flow of blood between the heart and lungs. Blood that returns from the systemic circuit is received in the right atrium of the heart via the superior and inferior venae cavae and the coronary sinus. This blood is low in oxygen and high in carbon dioxide. It then moves into the right ventricle, which pumps it through the pulmonary trunk into the right and left pulmonary arteries toward the lungs.
In the lungs, the blood travels through the pulmonary capillaries where gas exchange occurs within the lung alveoli, allowing oxygen to enter the blood and carbon dioxide to be expelled. Following this gas exchange, the now oxygen-rich blood flows from the pulmonary capillaries into the pulmonary venules and then into the larger pulmonary veins. Ultimately, four pulmonary veins (two from each lung) return the oxygenated blood back to the left atrium of the heart, completing the pulmonary circuit and preparing the blood for the systemic circuit via the left ventricle.