The normal heart sound consists of two distinct sounds: "lub" (S1) and "dub" (S2).
Here's a breakdown:
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S1 (Lub): This is the first heart sound and is caused by the closure of the mitral and tricuspid valves (the atrioventricular valves) at the beginning of ventricular systole (contraction).
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S2 (Dub): This is the second heart sound and is caused by the closure of the aortic and pulmonic valves (the semilunar valves) at the beginning of ventricular diastole (relaxation).
Essentially, the "lub-dub" sequence represents one complete heartbeat cycle. Doctors listen to these sounds with a stethoscope to assess the health of the heart valves and identify any potential abnormalities. Additional sounds, like murmurs, can indicate heart problems.
