3rd hea sound is d/t

A soft, low-pitched third sound is heard about one-third of the way through diastole in many normal young individuals. It coincides with the period of rapid ventricular filling and is probably due to vibrations set up by the inrush of blood. Ref: Ganong's Review of medical physiology 25th edition. Page:542 first sound-beginning of systole- Causes- sudden closure of av valves. Rapid increase in tension in the ventricular muscles during isometric contraction acting on filled ventricles. Turbulence created in the blood due to ventricular contraction. second sound-end of clinical systole - closure of semilunar valves. Rush of blood into the ventricles due to opening of AV valves contributes. Third sound- vibration setup in the ventricle during the early period of rapid ventricular filling. fouh sound- causes-atrial contraction. Vibration setup within the ventricle due to inflow of blood produced by atrial systole.