What are the two heart sounds heard through stethoscope?

cbse
circulation

#1

What are the two heart sounds heard through stethoscope? How is each of these produced?
Or
What are two heart sounds? When and how are these sounds produced?
Or
Explain heart sounds.


#2

We can hear with a stethoscope, the two main heart sounds (i.e., lub and dub), which repeat rhythmically. These sounds result from the closure of the heart valves. The first sound (lub), which is of longer duration (0.16-0.90 s) and a louder one is created by the closure of the atrio-ventricular valves immediately after the start of the ventricular systole. The second sound is of shorter duration (0.10 s) and is created by the closure of the semilunar valve at the end of the ventricular systole.