Question

briefly describe the cause of the turbulence associated with each of the 4 heart sounds:

1st heart sound 2nd heart sound 3rd heart sound 4th heart sound

Answer 1

Heart sounds are the noises generated by the beating heart and the resultant flow of blood through it.

CAUSE:

First heart sound (S1)

It is caused by the closure of the atrioventricular valves, i.e. tricuspid and mitral (bicuspid), at the beginning of ventricular contraction, or systole.

Second heart sound (S2)

It is caused by the closure of the semilunar valves (the aortic valve and pulmonary valve) at the end of ventricular systole and the beginning of ventricular diastole.

Third heart sound (S3)

Rarely, there may be a third heart sound also called a protodiastolic gallop, ventricular gallop.

S3 is thought to be caused by the oscillation of blood back and forth between the walls of the ventricles initiated by blood rushing in from the atria. The third heart sound is benign in youth, some trained athletes, and sometimes in pregnancy but if it re-emerges later in life it may signal cardiac problems, such as a failing left ventricle as in dilated congestive heart failure (CHF).

Fourth heart Sound (S4)

S4 when audible in an adult is called a presystolic gallop or atrial gallop. This gallop is produced by the sound of blood being forced into a stiff or hypertrophic ventricle.

It is a sign of a pathologic state, usually a failing or hypertrophic left ventricle, as in systemic hypertension, severe valvular aortic stenosis, and hypertrophic cardiomyopathy. The sound occurs just after atrial contraction at the end of diastole and immediately before S1.