a normal heart, the right side of the heart is completely separate from the left side. At the chambers and openings of the heart are a series of one-way (non-return) valves that maintain the direction of circulation. The heart beats an average of 60 to 80 beats per minute in an average adult at rest. It pumps approximately 6 liters of blood per minute. The heart can increase this flow by several times when needed through increasing the number of beats per minute and the force of the heart contractions.