The Cardiac Cycle - Essay Example

We are going to trace the blood to and from the heart. The blood starts its passage from the right atrium that has two major veins - the Superior vena cava that receives the deoxygenated blood from the upper parts of the body like the head and arms, and the Inferior vena cava that gets deoxygenated blood from the lower parts of the body like the torso and the legs. The blood entering the right ventricle of the heart from these two major veins through the tricuspid valve is filled with carbon – dioxide.

From the right ventricle, the deoxygenated blood is carried through the pulmonic valve to the pulmonary artery into the lungs. The blood is freed from impurities by the removal of carbon – dioxide and the addition of oxygen and once again passes through the pulmonary veins and empties itself into the left atrium. The chamber that receives the oxygenated blood from the lungs through the pulmonary veins is the left atrium. Between the left atrium and the left ventricle is a valve called the mitral valve or bicuspid valve, which helps to regulate the flow of blood into the left ventricle.

Both the bicuspid valve and the tricuspid valve also called the atrioventricular (AV) valves simultaneously open and close producing a Lub – Dub sound, which is the heartbeat of a person. The Lub sound is the opening of the valves and the Dub sound is the closing of the valves. The largest and most important of all the four chambers is the fourth chamber of the left ventricle which is the strongest pump that helps to discharge blood into the aorta through a valve called the aortic valve.

Both the pulmonary and the aortic valve operate simultaneously with each other. The aorta then takes the oxygenated blood and sends it to all the different parts of the body. In the same way, the bicuspid and tricuspid valves also open up simultaneously permitting blood to flow into the ventricles. When this happens, they contract and eject blood into the lungs and the body. In the meantime, the atria relax and once again fill with blood.