The heart contains 4 valves. They are the aortic, pulmonary, tricuspid, and mitral valves. The valves open and close to keep blood moving in the right direction through the heart. As the heart beats, blood moves through it. With each squeeze, the valves open and close to keep blood moving forward. In this way, valves keep blood moving as efficiently as possible through the heart.
When the heart relaxes between beats:
Oxygen-rich blood from the lungs fills the left atrium.
Oxygen-poor blood from the body fills the right atrium.
When the atria beat:
The left atrium squeezes, pushing blood through the mitral valve into the left ventricle.
The right atrium squeezes, pushing blood through the tricuspid valve into the right ventricle.
When the ventricles beat:
The left ventricle squeezes, pushing blood through the aortic valve out to the coronary arteries, the brain, and body.
The right ventricle squeezes, pushing blood through the pulmonary valve to the lungs.