How your heart works: two pumps, one spark, and what a heart attack really is
The two pumps of your heart: why your blood passes through it twice
Your heart looks like one pump. It is really two, joined side by side, and your blood goes through it twice on every trip around your body. Where does it go in between?
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1
Let's shrink down and ride with one red blood cell. It just came back from your feet, where it gave some of its oxygen to your muscles. We draw it teal for that.
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2
It goes into the right side of your heart. One squeeze, and out it goes again. But not to your body: the right side pumps only to your lungs.
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3
In your lungs, the cell picks up fresh oxygen and turns bright red. Then it goes straight back to the heart.
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This time it enters the left side. The left side pumps it out through a big artery, the aorta, to your whole body: your brain, your arms, your dancing feet.
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So your heart is two pumps, side by side. On each trip around your body, your blood passes through it twice.
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Each pump has two rooms. Blood comes into a small room on top, the atrium. It drops into a big room below, the ventricle, which squeezes it out.
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The lungs are close, so the right pump has an easy job. The left pump sends blood to your whole body. It pushes about five times harder, and its wall is much thicker.
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Still, at each beat both pumps send out the same amount, about a small cup. If one sent more, blood would pile up on one side.
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Both pumps squeeze at the same moment, about once a second, all your life. Something must give them the signal.
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Quick check
A red blood cell leaves your brain.
Show the answer
The right side, because it comes back from the body. Then it goes to your lungs, back to the left side, and only then out to your body again.
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Go further
A few words about the tubes of the blood.