How does the heart work step by step?
The heart as a pump The heart is a pump that rhythmically contracts and relaxes. Think of the principles at work in a hand operated water pump. When the handle is depressed, pressure is put on the water and it exits through a spigot. When the handle is raised, a vacuum is created and water is drawn in from the well. The flow of the water forces open a little “trap door,” a valve, which opens in one direction only. Once the water is drawn up into the pumping apparatus, it cannot flow backward into the well, only outward to the spigot. This is the way the heart works. It is the pump in charge of circulating oxygen, water, and nutrients through the bloodstream to all of the body’s tissues, including its own. The heart wall is a muscle, and just like any other muscle, it needs oxygen, water, and nutrients to function. But unlike other muscles for example, the ones in the arms or legs, which, when resting, need only a little oxygen the heart muscle needs a good supply of oxygen every s...