How the heart and blood vessels deliver oxygen — Health, 14–17 years
Learn how the heart, blood and blood vessels work together to supply cells and carry away waste.
The heart is a delivery pump
Your heart pushes blood through a branching network of vessels. Blood takes oxygen from the lungs to working cells, then carries carbon dioxide back to the lungs. It also transports nutrients, heat and chemical messages, so circulation links many parts of the body.
Why a circulation system is needed
A large body cannot rely on oxygen and food simply drifting from the outside to every cell. Cells are too far from the lungs and digestive system, and wastes must be removed quickly. A pump and vessel network solve this distance problem by keeping supplies moving.
What happens during a sprint
Imagine sprinting for 20 seconds. First, your muscles use more oxygen and produce more carbon dioxide. Your brain signals the heart to beat faster; for example, a pulse rising from 70 to 150 beats per minute sends more blood through the muscles. You breathe faster too, bringing fresh oxygen in.
The heart does not make oxygen
It is easy to think that a stronger heartbeat creates more energy, because exercise makes the heart pound and you feel warmer. But the heart is a pump, not a factory for oxygen or energy. The lungs load oxygen onto the blood, while cells release energy from fuel using that oxygen.
Reading a pulse
A pulse is the pressure wave made when the heart pushes blood into an artery. You can gently feel it at the wrist or side of the neck, count beats for 30 seconds and double the number. This can help compare resting and exercising heart rate, but unusual symptoms need medical advice.
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