How your heart works: two pumps, one spark, and what a heart attack really is
Coronary arteries: how your heart feeds itself
Your heart is full of blood all day, and still its thick wall cannot feed on it. It feeds through a few small arteries of its own. What happens to a heart when one of them closes?
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Your heart never stops, so it needs a lot of oxygen. And its left side is always full of fresh blood. Easy, you might think: it just drinks from the inside.
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But the wall of the heart is too thick. Oxygen from the blood inside reaches only the thin inner layer. The rest of the muscle would starve.
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So the heart feeds from the outside, like any other muscle. Its own small arteries run over its surface: the coronary arteries.
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They branch off at the very first spot they can: the start of the aorta, right where it leaves the heart. Your heart serves itself first.
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Strangely, when the left ventricle squeezes, it pinches its own small arteries. Its muscle gets most of its blood between beats, when it relaxes.
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The arteries split into smaller and smaller branches. Each branch feeds its own patch of muscle.
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If one of these arteries closes, the patch of muscle it feeds gets almost no blood. That is a heart attack. At the end of the class, Miva's uncle stops, pale, a hand on his chest. How can an artery close, inside a living body?
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Quick check
A heart that beats very fast.
Show the answer
It gets less time to flow in. The muscle is fed mostly between beats, so shorter rests mean less time to fill its arteries, just when it works hardest.
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Go further
Two names for the curious.