The average heart pumps over 100 gallons (nearly 400 liters) of blood every hour. Your heart is a very powerful, well-designed machine which has a series of chambers connected through valves to keep blood moving in the right direction.
Blood is intended to go through your heart in only one direction. Heart valves play key roles in this one-way blood flow, opening and closing with each heartbeat. Pressure behind and in front of the valves allows them to open their flaps (known as cusps or leaflets) at precisely the right time, then close them snugly to prevent a backflow of blood.
How Blood Moves Through Your Heart
There are four valves in the heart. They include the mitral and aortic valve on the left side and the tricuspid and pulmonic valve on the right side.
Blood without oxygen returns from the body and flows into the heart's upper-right chamber (the right atrium). Next, it goes through the tricuspid valve into the lower-right chamber (the right ventricle). The right ventricle (the muscular part of the heart) pumps the blood through the pulmonary valve and into the lungs. While in the lungs, the blood gains oxygen and gives up carbon dioxide, which is exhaled. As the right ventricle is pushing blood through the pulmonary valve, the tricuspid valve closes to stop blood from flowing back into the right atrium.
Oxygen-loaded blood returning from the lungs flows into the upper-left chamber (the left atrium). This blood enters the mitral valve into the powerful and muscular lower-left chamber (the left ventricle), with the mitral valve preventing the backflow of blood.
At the same time that the right ventricle is pumping the blood without oxygen into the lungs, the left ventricle is pushing the blood with oxygen through the aortic valve and on to all of the body's organs. It does this with plenty of force to ensure blood enters your brain and even your toes!
Problems with Valves
Two types of problems can occur when blood flows though the valves: regurgitation or stenosis.
Regurgitation is also called insufficiency or incompetence. Regurgitation occurs when a valve doesn't close properly and blood leaks backward instead of moving forward. If too much blood flows backward, only a small amount can travel forward to your body's organs. If this goes on for a long time, your heart tries to work harder, but with time your heart will become enlarged (dilated) and less able to pump blood through your body.
Stenosis (tightness) happens when the leaflets do not open wide enough and only a small amount of blood can flow through the valve. Stenosis occurs when the leaflets thicken, stiffen, or fuse together. Because of the narrowed valve, your heart must work harder to overcome the tight opening in the stenosed valve to move blood through your body.