Blood enters the right side of the heart via the inferior and superior vena cava and the left side of the heart via the pulmonary vein. It empties from the heart via the pulmonic valve on the right and the aortic valve on the left.
The heart is made up of atria, ventricles, arteries, veins and valves. The atria and ventricles perform the pumping action, while the valves regulate blood flow. When the valves work properly, blood flows in only one direction. Both sides of the heart work together to ensure there is always an adequate supply of oxygen-rich blood available to the rest of the body.
On the right side of the heart, oxygen-poor blood enters through the inferior and superior vena cava before emptying into the right atrium. The blood then travels from the right atrium through the tricuspid valve and into the right ventricle. Blood leaves the right side of the heart via the pulmonic valve and empties into the pulmonary artery.
Oxygenated blood travels from the pulmonary vein to the left atrium. Then it flows through the mitral valve and into the left ventricle. Finally, it passes through the aortic valve and into the aorta. From there, the blood is pumped to other parts of the body.