Explain heart sounds.

Heart sounds are noises generated by the closing and opening of the heart valves. In a healthy individual, there are two normal heart sounds called lub and dub. Lub is the first heart sound. It is associated with the closure of the tricuspid and bicuspid valves at the beginning of systole. The second heart sound dub is associated with the closure of the semilunar valves at the beginning of diastole.
These sounds provide important information about the condition and working of the heart.

 Lub and Dub Sounds: Two prominent sounds are produced during each cardiac cycle. These sounds can be easily heard through a stethoscope. The first sound is called lub and is associated with the closure of the tricuspid and bicuspid valves. The second sound is called dub and is associated with the closure of the semi-lunar valves. These sounds are important for clinical diagnosis. 

During each cardiac cycle two prominent sounds lub and dub are heard. The first heart sound (lub) is associated with the closure of the tricuspid and bicuspid valves which extends for 0.16 – 0.9 sec. The second heart sound (dub) is associated with the closure of the semilunar valves and extends for 0.10 sec.