The familiar "lub-dub" sound isn't the heart muscle contracting, nor is it blood simply sloshing around. It is the sound of heart valves snapping shut .
The heart doesn't "beat" — it valves shut. The "lub" is the sound of the top valves closing as the bottom chambers squeeze. The "dub" is the sound of the exit valves closing as the bottom chambers relax. why does the heart make a lub dub sound
Think of it like clapping your hands: the sound isn't from the movement itself, but from the instant two surfaces meet. In the heart, that meeting is the forceful closure of valves designed to keep blood flowing in one direction. The familiar "lub-dub" sound isn't the heart muscle
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