Pediatric Diseases and ConditionsAnatomy and Function of the Heart Valves
The heart consists of four chambers, two atria (upper chambers) and two ventricles (lower chambers). There is a valve through which blood passes before leaving each chamber of the heart. The valves prevent the backward flow of blood. These valves are actual flaps that are located on each end of the two ventricles (lower chambers of the heart). They act as one-way inlets of blood on one side of a ventricle and one-way outlets of blood on the other side of a ventricle. Normal valves have three flaps, except the mitral valve, which has two flaps. The four heart valves include the following:
tricuspid valve: located between the right atrium and the right ventricle
pulmonary valve: located between the right ventricle and the pulmonary artery
mitral valve: located between the left atrium and the left ventricle
aortic valve: located between the left ventricle and the aorta
As the heart muscle contracts and relaxes, the valves open and shut, letting blood flow into the ventricles and atria at alternate times. The following is a step-by-step illustration of how the valves function normally in the left ventricle:
After the left ventricle contracts, the aortic valve closes and the mitral valve opens, to allow blood to flow from the left atrium into the left ventricle.
As the left atrium contracts, more blood flows into the left ventricle.
When the left ventricle contracts, the mitral valve closes and the aortic valve opens, so blood flows into the aorta.
Heart valves can have one of two malfunctions:
regurgitation (or leakage of the valve)
The valve(s) does not close completely, causing the blood to flow backward through the valve. This results in leakage of blood back back into the atria from the ventricles (in the case of the mitral and tricuspid valves) or leakage of blood back into the ventricles (in the case of the aortic and pulmonary valves).
stenosis (or narrowing of the valve)
The valve(s) opening becomes narrowed or valves become damaged or scarred (stiff), inhibiting the flow of blood out of the ventricles or atria. The heart is forced to pump blood with increased force in order to move blood through the narrowed or stiff (stenotic) valve(s).
Heart valves can have both malfunctions at the same time (regurgitation and stenosis). Also, more than one heart valve can be affected at the same time. When heart valves fail to open and close properly, the implications for the heart can be serious, possibly hampering the heart's ability to pump blood adequately through the body. Heart valve problems are one cause of heart failure.