Anatomy and Function of the Heart Valves - Stanford Hospital & Clinics

Cardiovascular Diseases

Anatomy and Function of the Heart Valves

What are 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. Each valve actually has 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.

How do the heart valves function?
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 again, the mitral valve closes and the aortic valve opens, so blood flows into the aorta.

What is heart valve disease?
Heart valves can have one of two malfunctions:

regurgitation
The valve(s) does not close completely, causing the blood to flow backward instead of forward through the valve.
stenosis
The valve(s) opening becomes narrowed or does not form properly, inhibiting the ability of the heart to pump blood to the body due to the increased force required to pump blood through the stiff (stenotic) valve(s).

Heart valves can have both malfunctions at the same time (regurgitation and stenosis). 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.

For more information, please contact the Stanford Health Library