The heart acts as a pump. It is divided in to a right and left portion. The right portion receives blood (which is impure) from the body and pumps the same to the lungs for purification (oxygenation). The impure blood enters the heart from two large veins called the superior and inferior vena cava. The blood from these veins enters the right upper chamber known as the Right Atrium. This chamber also receives impure blood from the heart veins through the coronary sinus. The right atrium pumps this blood into the Right Ventricle or the right lower chamber through the Tricuspid Valve. The tricuspid valve prevents blood from flowing from the right ventricle to the right atrium. The right ventricle pumps blood into the Pulmonary Artery. The Pulmonary Valve prevents blood from leaking back into the right ventricle. The pulmonary artery carries impure blood to the right and left lungs. The left half of the heart collects and pumps pure (oxygenated) blood from the lungs to all parts of the body. The blood from the lungs enters the heart from four veins called the Pulmonary Veins. These veins bring the blood into the left upper chamber called the Left Atrium. The left atrium pumps blood through the Mitral Valve into the left ventricle or left lower chamber.
The Mitral valve prevents blood from leaking back from the left ventricle to the left atrium. The left ventricle pumps the blood into the Aorta, which circulates to all parts of the body. The Aortic Valve prevents blood from leaking back into the left ventricle. The four valves in the heart are the Mitral and Aortic valves on the left side and Tricuspid and Pulmonary valves on the right side.