Which action of the heart makes the first of the "lup-dup" sounds?
A) closing of the atrioventricular valves
B) closing of the pulmonary valve
C) closing of the aortic valve
D) the contraction of the left ventricle
E) the contraction of the right ventricle

Question

Quizplus · Accepted Answer

The first sound of the "lup-dup," often described as "lub," is caused by the closing of the atrioventricular valves (the mitral and tricuspid valves) at the beginning of ventricular systole. This sound is associated with the start of the contraction of the ventricles, preventing backflow of blood into the atria.

Which Action of the Heart Makes the First of the "Lup-Dup