Video narration
How does blood travel from your body to your lungs, then return to your body? Think of a household water pump pushing water through connected pipes: the heart keeps blood moving along a route. After delivering oxygen around your body, blood returns carrying less oxygen and more carbon dioxide. It flows through veins-vessels that carry blood toward the heart-and reaches the heart's right side. Here's the turn: the heart sends it to your lungs. There, blood releases carbon dioxide and picks up oxygen, then returns to the heart's left side. The left side pumps it out through arteries, vessels that carry blood away from the heart, sending oxygen-rich blood around your body. As your body uses oxygen, blood returns through veins, and the route begins again. So, each heartbeat keeps one loop going: oxygen out to your body, carbon dioxide back.