Blood is pumped out under great force from the left ventricle. It leaves via the body's main blood vessel the aorta. This artery branches as it progresses in order to convey freshly oxygenated blood throughout the body. The left ventricle has the thickest heart muscle in order to accommodate the force needed to pump the blood around the body.
The de-oxygenated blood from the whole body enters the heart into the upper right chamber, called the right atrium. The blood enters here through the vessel called the superior vena cava. The atrium contracts to let the blood enter into the right ventricle after passing through the tricuspid valve. The tricuspid valve has three flaps that allow easy flow of blood.
When the right ventricle contracts the flaps close the atrium. Therefore the backward flow of blood into the atrium is stopped.
The blood leaves the ventricle by the pulmonary arch. Upon leaving the heart, this arch divides into two pulmonary arteries. These arteries lead to each of the lungs. In this case, the backward flow of blood is prevented by the semi-lunar valves in the pulmonary arch.
The pulmonary veins take the oxygenated blood from the lungs the heart. These veins lead to the left atrium of the heart. Contraction of the left atrium sends the blood into the left ventricle of the heart. The bicuspid valves between the two left chambers prevent the backward flow of blood. This valve has two flaps that regulate the flow of blood. The left ventricle contracts to force the blood out of the heart through the aortic arch. Blood in pumped to all parts of the body through the aortic arch.
