Why are there four valves in the heart?

There are not four, but two sets of valves in the human heart—four valves, two on each side of the heart. The right side of the heart has the tricuspid valve and the pulmonary valve. The left side of the heart has the mitral valve (also known as the bicuspid valve) and the aortic valve.

1. Tricuspid valve: This valve is located between the right atrium (upper chamber) and the right ventricle (lower chamber) and is made up of three cusps or flaps. It prevents blood from flowing back from the ventricle to the atrium during ventricular contraction.

2. Pulmonary valve: Located between the right ventricle and the pulmonary artery, which carries blood from the heart to the lungs, the pulmonary valve is made up of three cusps. It prevents blood from flowing back into the ventricle from the pulmonary artery.

3. Mitral valve (or bicuspid valve): Situated between the left atrium and left ventricle, this valve is made up of two cusps and prevents the backflow of blood from the ventricle into the atrium during ventricular contraction.

4. Aortic valve: Located between the left ventricle and the aorta, the main artery that supplies oxygenated blood to the body, the aortic valve is composed of three cusps or leaflets and prevents blood from flowing back into the ventricle from the aorta.

These four valves are essential for the proper functioning of the human heart. They ensure the one-way flow of blood, preventing backflow and allowing the heart to pump blood effectively.