Theory heart sound

Primary heart sounds

First heart sound (S1)
-produced by closing effect of tricuspid and mitral valves. at the beginning of ventricular systolic.
-heart tone S1, forms the "lub" of "lub-dub"

Second heart sound (S2)
-represents the vibrations as a result from closure of semilunar valves beginning the aortic valves and  pulmonary valve.
-heart tone S2,  forms the "dub" of "lub-dub"

Extra heart sounds

Third heart sound (S3)
- result of tensing of the chordae tendineae during rapid filling and expansion of the ventricle.
-heart tone S3, from the "lub-dub-ta" or "slosh-ing-in"

Fourth heart sound (S4)
- produced by the sound of blood being forced into a stiff/hypertrophic ventricle.
-heart tone s4, from the "ta-lub-dub" or "a-stiff-wall"