What makes lub-dub heart beat sound?

Question

The opening and closing of the valves in your heart.

Your muscles contracting.

Blood cells passing through the lungs.

Answer 1

Incorrect. The lub-dub sound is created by the closing of the heart valves, specifically the mitral and tricuspid valves (first sound, "lub") and the aortic and pulmonary valves (second sound, "dub"). The heart muscle contracting also plays a role in the heart's pumping action, but it does not directly create the lub-dub sound. Blood cells passing through the lungs also do not directly contribute to the heart sound.