It is a muscle that contracts regularly and continuously to distribute blood throughout the body. Blood brings oxygen and other nutrition products such as glucose, trace elements, vitamins … fueling the cells and without which they can live. 

The heart works like a pump

A pump is an engine that aspires liquid upstream and the downstream rejects. It is necessary that the motor functions of course, that there is liquid upstream and downstream pipes and upstream are of good quality, there is no obstacle on the circuit. In a living organism, the heart is the pump, the blood is pumped liquid and rejected, the pipes are on the one hand, the veins that bring blood upstream and on the other hand, the arteries that reject the blood downstream. What complicates things a bit is that the heart is composed of two pumps, a heart left and a right heart with two circuits: the large and small circulation. The great movement: the left heart feeds the whole body with a red blood rich in oxygen from the lungs. When it comes to red blood cell level bodies, it exchanges the element oxygen, carbon dioxide against, cellular waste. The red blood becomes "black", at least darker and goes right to the heart. The small movement: the right heart replant the black blood in charge of carbon dioxide in the lungs so that it recharges again in oxygen and returned to the left heart and circulation.