The Lub sound is produced by closing of which valves?

The Lub sound is produced by closing of which valves?

• A. Closing of the Atrioventricular Valves
• B. Closing of the Semilunar Valves
• C. Opening of the Atrioventricular Valves
• D. Opening of the Semilunar Valves

Answer: (A)

The Lub sound marks the start of ventricular systole. It happens when the atrioventricular valves (the mitral and tricuspid valves) close as the ventricles contract and pressure rises. This rapid snap shuts the valves and the associated vibrations create the characteristic “lub.” The second heart sound, “dub,” comes later when the semilunar valves (the aortic and pulmonary valves) close at the end of systole as the ventricles relax. Opening of either set of valves wouldn’t produce these sounds in this normal sequence.

The Lub sound marks the start of ventricular systole. It happens when the atrioventricular valves (the mitral and tricuspid valves) close as the ventricles contract and pressure rises. This rapid snap shuts the valves and the associated vibrations create the characteristic “lub.” The second heart sound, “dub,” comes later when the semilunar valves (the aortic and pulmonary valves) close at the end of systole as the ventricles relax. Opening of either set of valves wouldn’t produce these sounds in this normal sequence.