The first heart sound is heard when the
A)AV valves open.
B)AV valves close.
C)semilunar valves close.
D)atria contract.
E)blood enters the aorta.

Name: The first heart sound is heard when the A)AV valves open. B)AV valves close. C)semilunar valves close. D)atria contract. E)blood enters the aorta.
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Question

Quizplus · Accepted Answer

The first heart sound is known as the "lub" sound and is produced by the closure of the AV (atrioventricular) valves (the tricuspid and mitral valves) as the ventricles begin to contract.

The First Heart Sound Is Heard When the