The human heart is large, hollow muscle that pumps the blood to every part of the body. The heart has four chambers, or 'rooms' , and valves that control the flow of blood. A simple model that you can make shows how the heart pump works. Cut a small hole in a hollow rubber ball. Squeeze the ball press your hands around it, to force the air out of it. Then hold the flattened ball in a pan of water. Let go so that the ball can fill with water. Squeeze the ball again, and watch the water squirt that is to say it go out through the hole of the ball. This show how the heart fills with blood and then pumps is out again.-------------
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Definition of the human heart is