How the heart and blood carry oxygen — Health, 7–10 years
The heart is a pump that keeps blood moving around the body. Blood delivers oxygen and useful materials, then carries away some waste.
The heart is a pump
Your heart squeezes and relaxes again and again, pushing blood through tubes called blood vessels. The blood reaches your muscles, brain and other organs, bringing oxygen and useful substances. It then returns to the heart to make another journey.
Why blood must keep moving
Every living cell needs supplies, especially oxygen, but the body cannot store enough of them beside every cell. It also needs waste carried away. Circulation solves both problems by making a delivery and collection route that works all the time.
After running
Count your pulse for 15 seconds, then multiply by four. If you count 30 beats, your pulse is about 120 beats per minute. After sitting quietly for a few minutes, count again: it will often be lower because your muscles need less oxygen.
A faster heartbeat is not always danger
It is easy to think that a fast heartbeat means something is wrong, because we notice it strongly. Usually it is a sensible response to running, excitement or fear: muscles need more oxygen, so the heart speeds up. It should settle when the cause ends.
At the doctor’s
A nurse may measure your pulse or blood pressure to learn how your circulation is working. Sports watches also estimate pulse during exercise, but they are not perfect. A number is useful information, not a complete answer about health.
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