Multiple choice

What causes the first heart sound or the "lub"?

  1. The sound of blood rushing out of the ventricles

  2. The closing of the mitral and tricuspid valves

  3. The closing of the pulmonary and aortic valves

  4. The sound of blood rushing into the auricles

  5. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The first heart sound or "lub" results from closure of the tricuspid and mitral valves.

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