The major heart sounds are normally created by:
A) valves opening.
B) valves closing.
C) the rapid movement of blood.
D) rubbing together of the cardiac walls.

Question

Quizplus · Accepted Answer

At the beginning of systole, ventricular contraction raises the pressure in the ventricles and forces the mitral and tricuspid valves closed, which produces the first heart sound S₁, "lub." When the pressure in the ventricles falls, below that of the aorta and pulmonary artery, and when the ventricles are almost empty, the aortic and pulmonic valves close, producing the second heart sound S₂, "dub." Valve opening is usually a silent event.

The Major Heart Sounds Are Normally Created By