Which of the following indicates the first and second heart sound in the correct order a. Atrioventricular valve closure — semilunar valve closure b. Ventricular diastole — atrioventricular valve closure c. Atrial systole — ventricular systole d. Ventricular systole — semilunar valve closure
Question
Which of the following indicates the first and second heart sound in the correct order a. Atrioventricular valve closure — semilunar valve closure b. Ventricular diastole — atrioventricular valve closure c. Atrial systole — ventricular systole d. Ventricular systole — semilunar valve closure
Solution
The correct answer is a. Atrioventricular valve closure — semilunar valve closure.
Here's why:
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The first heart sound (S1) is caused by the closure of the atrioventricular valves (mitral and tricuspid) at the beginning of ventricular contraction, or systole. This prevents the backflow of blood into the atria.
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The second heart sound (S2) is caused by the closure of the semilunar valves (aortic and pulmonic) at the end of ventricular systole. This prevents the backflow of blood into the ventricles.
So, the correct order of events that corresponds to the first and second heart sounds is the closure of the atrioventricular valves followed by the closure of the semilunar valves.
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