In the circulation of oxygen, which sequence correctly describes the path from the lungs to the body's tissues?

• A. Lungs, arteries, capillaries, cells, veins
• B. Lungs, heart, artery, cells, veins
• C. Lungs, heart, veins, arteries, cells
• D. Lungs, arteries, heart, veins, cells

Answer: (B)

Oxygenated blood moves from the lungs to the heart first, because the heart acts as the pump that sends blood into the systemic circulation. Once blood is in the heart, it’s propelled into the systemic arteries, which carry it away from the heart to the tissues. There, blood travels through capillaries to reach the cells and deliver oxygen; after gas exchange, the blood returns through the veins back toward the heart to begin the cycle again. So the path from lungs to tissues is lungs, heart, arteries, cells (via capillaries), veins. This ordering reflects how oxygen is picked up in the lungs, driven by the heart into the body’s tissues, and then returned to the heart for re-oxygenation. Choices that skip the heart between the lungs and systemic circulation or mix up the direction of vessels don’t fit how this circulation works.