Final answer:
All four pulmonary veins, which carry oxygen-rich blood from the lungs, enter the left atrium of the heart, completing the pulmonary circulation part of blood circulation.
Step-by-step explanation:
The student is asking about the path of blood flow in the pulmonary circulation. After gas exchange in the lungs, the oxygen-rich blood is carried through a series of vessels, including pulmonary venules and veins, back to the heart. Specifically, all 4 pulmonary veins will enter the left atrium of the heart.
In the pulmonary circuit, deoxygenated blood is pumped from the right ventricle into the right and left pulmonary arteries towards the lungs. Once oxygenated, blood returns to the heart via the pulmonary veins. The left atrium then receives this oxygenated blood, which is subsequently pumped into the left ventricle and out to the systemic circulation.
To summarize, the pulmonary circuit starts with deoxygenated blood being pumped from the heart to the lungs for oxygenation. After receiving oxygen in the lungs, blood returns to the heart via the pulmonary veins, completing the circuit by entering the left atrium.