Question

When are the sounds “LUBB” and “DUP” produced respectively during heart beat?

Answer 1

We know that blood constantly moves through the four chambers of heart coming through the vein into right atrium ----> Right ventricle -----> Pulmonary artery ------> Lungs

And then in,

Pulmonary veins ----> Left atrium --> Left ventricle--> Aorta

In every step some valves open and some closes. Valves are communicating doors that when open allows blood to pass through and when closed hold blood within a chamber.

Heart has four valve:

Two Atrioventricular valve which separates the Atria from ventricle and those are:

1: Tricuspid valve. This valve is located between the right atrium and the right ventricle.

2: Mitral valve. This valve is located between the left atrium and the left ventricle. It has only 2 leaflets.

And two Semilunar valve that is:

3: Pulmonary valve. The pulmonary valve is located between the right ventricle and the pulmonary artery

4: Aortic valve. The aortic valve is located between the left ventricle and the aorta.

When these valves closes they make sound that is transmitted in the direction of blood flow.

When blood fills the relaxed ventricle (diastole) both the atrioventricular valve ( Mitral valve and Tricuspid valve) snaps shut creating a long loud sound “ LUBB” this is the first heart sound ( S1) .

When the ventricles contract and push blood out ( Systole) semilunar valves gets closed making a sharp sound called “DUBB”. This “dubb” is a second heart sound.

The first heart sound or "lub" results from closure of the tricuspid and mitral valves.

The second heart sound, or "dub," marks the beginning of ventricular diastole. It is produced by closure of the aortic and pulmonary (pulmonic) semilunar vains when the intraventricular pressure begins to fall.