Video narration
How does oxygen from one breath reach all the way to your toes? Think of blood as a delivery route: it picks up oxygen in your lungs, then carries it onward. First, blood returning from your body enters the heart's right side, and the heart sends it to the lungs. There, blood picks up oxygen from the air you breathed in and lets go of carbon dioxide brought back from your body. But the lungs aren't the destination: blood returns to the heart's left side, which pumps it out around your body. As blood travels, it delivers oxygen to the parts of you that need it. Then, after delivery, it returns from your body to the heart and heads to the lungs again. So oxygen reaches your toes because your heart keeps this delivery loop going: lungs, heart, body, and back.