Difference between AV Valves and Semilunar Valves

Heart Valves

Heart valves function to make sure one-way flow of blood throughout the heart. Atrioventricular (AV) and semilunar valves are two types of valves present in the heart. These valves are flap-like structures that ensure the proper circulation of blood in the heart.

The valves are made up of endocardium and connective tissues. The opening and closing of the valves depend upon the pressure on either side of the valves. When the pressure on the backside of the valves is greater, they open, and the blood flows through; and when the pressure on the front side of the valves is greater, the valves are forced to shut.

Atrioventricular (AV) Valves

AV valves are situated between the atrium and ventricles on both sides of the heart. These valves allow the flow of blood from the atria to ventricles and also the backflow of blood into the atrium during systole.

The AV valve on the right is called the tricuspid valve that has three leaflets, and the valve on the left side is called the mitral or bicuspid valve that has two leaflets.

The atrial pressure increases when the ventricles relax, and as a result, the valves are pushed open, and the blood flows from atria to ventricles; conversely, the atrial pressure drops when the ventricles contract, forcing the flaps to shut and prevent the flow of blood.

Additionally, the valves are attached to fibrous connective tissues called chordae tendineae that prevent both the valves from inverting.

Semilunar Valves

Semilunar valves are located between the ventricles and the two major arteries. The aortic valve is present between the left ventricle and aorta, and the pulmonary valve is present between the right ventricle and pulmonary artery.

Both the valves allow easy flow of blood from the ventricles to both the arteries and prevent backflow at the same time. The semilunar valves are called so because they are shaped like a half-moon.

AV Valves

Semilunar Valves

Description

Atrioventricular valves are present between the arteries and ventricles.

Semilunar valves are present between the ventricles and major heart arteries.

Flow of Blood

It allows the flow of blood from the right atrium to the right ventricle and the left atrium to the left ventricle.

It allows the flow of blood from the left ventricle to the aorta and the right ventricle to the pulmonary artery.

Sound of the Heart

The closure of the valves makes the first sound of the cardiac cycle, “LUBB”

The closure of the valves makes the second sound of the cardiac cycle, “DUB”

Valves

The two valves are the tricuspid and mitral valves.

The two valves are aortic and pulmonary valves.

Special Feature

The AV valves are attached to connective tissue chordae tendineae that prevents the valves from inverting.

No such tissue is found.

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Frequently Asked Questions on Difference between AV Valves and Semilunar Valves

Do the AV and semilunar valves open at the same time?

No, the AV and semilunar valves never open at the same time.

Do the semilunar valves close during ventricular diastole?

Yes, the semilunar valves close during the ventricular diastole.

What makes the AV and semilunar valves open and close?

The pressure in front and behind the valves make the AV and semilunar valves open and close.

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