In the cardiac cycle, what does the S2 heart sound correspond to?

A. To pump blood to the lungs for oxygenation:
The right ventricle pumps deoxygenated blood to the lungs. The left ventricle is responsible for systemic circulation.

B. To receive deoxygenated blood from the body:
The right atrium receives deoxygenated blood from the systemic veins.

C. To regulate heart rhythm:
Heart rhythm is controlled by the SA and AV nodes and the conduction system, not the ventricles themselves.

D. To pump oxygenated blood into systemic circulation:
The left ventricle has thick muscular walls that generate the high pressure needed to pump oxygen-rich blood through the aorta and systemic arteries to the entire body. Dysfunction leads to decreased perfusion and signs of left-sided heart failure.

A. Atrial contraction:
Atrial contraction occurs just before ventricular systole and contributes minimally to heart sounds. The “lub-dub” of S1 and S2 does not correspond to atrial contraction.

B. Closure of the aortic and pulmonic valves:
The S2 heart sound (“dub”) occurs during ventricular diastole when the aortic and pulmonic valves close. This sound indicates the end of systole and the beginning of ventricular relaxation. It is best heard at the base of the heart.

C. Rapid filling of the ventricles:
Rapid ventricular filling occurs in early diastole and does not produce a normal heart sound. An abnormal sound (S3) can be associated with heart failure.

D. Closure of the mitral and tricuspid valves:
The closure of the mitral and tricuspid valves produces the S1 sound (“lub”), which marks the beginning of ventricular systole. Confusing S1 and S2 can lead to misinterpretation of cardiac auscultation.