The blueish color of the heart's right side stems from the oxygen-poor blood it contains. The left side of the heart collects the freshly oxygenated red blood from the lungs, and then pumps it out to the whole body. Once the body has absorbed the oxygen and other nutrients from the bloodstream, the blood returns to the right side of the heart and begins its journey again. The heart can perform these two vital tasks because it is a muscle. It pumps blood through muscular contractions, much the way you could squeeze toothpaste from a tube by a sharp squeezing motion in your hand.
Electrical pulses control the rate of the heart's contractions.
A healthy heart contract 55 to 85 times every minute. As well as being divided into halves, each side of the heart is divided into an upper and a lower section. The upper section is called an atrium. The atrium collects and stores the blood. The lower section is called the ventricle.