Anatomy and Function of the Heart Valves

By | December 11, 2023

What are heart valves?

The heart has 4 chambers, 2 upper chambers (atria) and 2 lower chambers (ventricles). Blood passes through a valve before leaving each chamber of the heart. The valves prevent the backward flow of blood. Valves are actually flaps (leaflets) that act as one-way inlets for blood coming into a ventricle and one-way outlets for blood leaving a ventricle. Normal valves have 3 flaps (leaflets), except the mitral valve. It only has 2 flaps. The 4 heart valves are:

  • Tricuspid valve. This valve is located between the right atrium and the right ventricle.
  • Pulmonary valve. The pulmonary valve is located between the right ventricle and the pulmonary artery.
  • Mitral valve. This valve is located between the left atrium and the left ventricle. It has only 2 leaflets.
  • Aortic valve. The aortic valve is located between the left ventricle and the aorta.

How do the heart valves work?

As the heart muscle contracts and relaxes, the valves open and shut. This lets blood flow into the ventricles and atria at alternate times. Here is a step-by-step description of how the valves work normally in the left ventricle:

  • When the left ventricle relaxes, the aortic valve closes and the mitral valve opens. This lets blood flow from the left atrium into the left ventricle.
  • The left atrium contracts. This lets even more blood to flow into the left ventricle.
  • When the left ventricle contracts, the mitral valve closes and the aortic valve opens. This is so blood flows into the aorta and out to the rest of the body.
  • While the left ventricle is relaxing, the right ventricle also relaxes. This causes the pulmonary valve to close and the tricuspid valve to open. This lets blood flow into the right ventricle that was returned to the right atrium from the body.
  • When the left ventricle contracts, the right ventricle also contracts. This causes the pulmonary valve to open and the tricuspid valve to close. Blood flows out from the right ventricle to the lungs before it is returned to the left atrium as fresh, oxygenated blood.
To open the closed walls of the heart