Question

Explain heart sounds.

Answer 1

During the cardiac cycle that is the circulation of blood through the chambers of the heart, the heart produces sound due to the closing and opening of the valves present in the atria and ventricles of both sides of the heart.

Complete answer:
The sounds ‘Lub-Dub’ are produced when we hear a heartbeat. After the contraction (systole) of the left atria, the blood is added to the left ventricle of the heart which increases the pressure in the left ventricle. As soon as the pressure in the left ventricle is more than the pressure in the left atria, the AV valve (Atrio- Ventricular valve) closes which makes the sound of ‘Lub’ or the first heart sound ${ s }_{ 1 }$. Then the blood flows into the aorta which increases the pressure of the aorta from the left ventricle. As soon as the pressure in the aorta is more than the pressure in the left ventricle, the Semilunar Valve (aorta valve) closes which makes the sound of ‘Dub’ or the second heart sound ${ s }_{ 2 }$.
- A heartbeat consists of systole and diastole of various chambers of the heart
- The systole and diastole during the cardiac cycle can be easily understood with the reference of ECG.
- The closing of the valve is necessary to avoid the backflow of blood in the left atria.
- The closing of the Semilunar valve is necessary to avoid the backflow of blood in the left ventricle.
- Low pressure can be considered as a low amount of blood in the chamber (for better understanding of the concept).

Note: Cardiac cycle refers to the characteristic changes in the pressure of the chambers of the heart and the movements of valves during contraction (systole) and relaxation (diastole) of various chambers of the heart. Low pressure can be considered as a low amount of blood in the chamber (for better understanding of the concept). The atrioventricular valve is present between the borders of the atrium and the ventricle. The semilunar Valve (aorta valve) is present between the borders of the left ventricle and the start of the aorta vessel.