How does the heart pump blood?

The explanation, step by step

1. 1. A muscle that never rests

   This is your heart, a fist-sized muscle that beats about a hundred thousand times a day. It is really two pumps side by side, working together in one squeeze.

2. 2. The right pump: to the lungs

   Let us cut it open: tired blue blood from the body arrives on the right side. The right ventricle squeezes it up the pulmonary trunk to the lungs for fresh oxygen.

3. 3. The left pump: to the body

   Bright red blood comes back from the lungs into the left side. See how thick the left wall is: it must push blood around the whole body. One mighty squeeze sends it up the aorta and out to every cell.

4. 4. Valves keep it one way

   Between the chambers, thin valves snap shut so blood never flows backwards. Fill, squeeze, fill, squeeze: two pumps in one beat keep you alive.

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