S2 is associated with -
Ans. is 'c' i.e., Closure of semilunar valves o S, is due to closure of semilunar valves (aortic and pulmonary valves).Feature1st heart sound2nd heart sound3rd heart sound4th heart soundCharacterLow pitched (frequency) slightly prolonged "lub"Shorter high pitched "dup"Soft low pitched weak rumblingArterial heart soundDuration0[?]14 second0[?]11 second0[?]1 second-Frequency25-45 Hz50 Hz-<20HzQCauseSudden closure of mitral & tricuspid valvesClosure of aortic & pulmonary' valvesRapid ventricular fillingQ d/t inthrusing of blood from atriaVentricular fillingQ d/t atrial contraction causing inthrushing of blood.TimingStart of ventricular systoleJust after end of ventricular systoleBegining of middle third of diastoleImmediately before 1st heart sound (presystolic)HeardS.1 & S2 can be heard with stethoscopeS1 & S4 can not be heard by stethoscope (ear) Q. So oftenly and S5 sometimes can be recorded in phonocardiorgam
Rapid ventricular filling
Atrial contraction
Closure of semilunar valves
Closure of AV valves
Circulation: Heart Valves and Heart Sounds;  Heart Defects