With Which of the Following is "Lubb-Dupp" Associated

Question

With which of the following is "lubb-dupp" associated?
A) Myocardial contraction
B) Ventricular depolarization
C) Closing of heart valves
D) Diffusion of O2 from the lungs to the blood in the pulmonary capillaries

Accepted Answer

"Lubb-dupp" is the sound of the closing of the heart valves. The first sound "lubb" is the closing of the atrioventricular valves (mitral and tricuspid), and the second sound "dupp" is the closing of the semilunar valves (aortic and pulmonary). Myocardial contraction (A) and ventricular depolarization (B) do not produce the sound. Diffusion of O2 from the lungs to the blood in the pulmonary capillaries (D) also does not produce any sound.