HEART SOUNDS
In all there are four heart sounds The first and the second heart sound are audible to the stethoscope as Lubb and Dubb They occur rhythmically at the beginning and end of the ventricular systole respectively
First Sound:
if occurs at the beginning of ventricular systole due to the closure of AV valves of both the ventricles synchronously it is muscular in origin The first sound is loud low pitched and of longer duration
Second Sound:
it occurs in the beginining of ventricular diastole due to closure of SL valves of pulmonary trunk and aorta synchronously it is valvular in origin the second sound is sharp shrill and of short duration
The third and fourth sounds are difficult to hear with the help of the stethoscope they are very low pitched third sound is caused by the sudden rush of atrial blood into the ventricles because ventricles are under diastolic condition fourth sound is caused by the contraction of atria consequent rush of blood into the ventricles
The heart beat is transmitted to the front wall of the chest in the fifth intercostal space medial to the left midclavicular plane by an upward and forward thrust of the apex of the heart if one puts his hand there the apex beat can be felt as a throb with every beat
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