AP BIOLOGY

Detailed explanation-1: -This sound comes from the valves shutting on the blood inside the heart. The first sound (the lub) happens when the mitral and tricuspid valves close. The next sound (the dub) happens when the aortic and pulmonary valves close after the blood has been squeezed out of the heart.

Detailed explanation-2: -Normal heart sounds come in pairs. The sounds are often described as a constant “lub-dub, lub-dub.” The first “lub-dub” is the sound of the mitral and tricuspid valves closing. The second “lub-dub” is the sound of the aortic and pulmonary valves closing soon after.

Detailed explanation-3: -Heart sounds are created from blood flowing through the heart chambers as the cardiac valves open and close during the cardiac cycle. Vibrations of these structures from the blood flow create audible sounds-the more turbulent the blood flow, the more vibrations that get created.

Detailed explanation-4: -There are two heart sounds every cardiac cycle, “lubb” and “dupp". “Lubb” is produced when the bicuspid and the tricuspid valves close shut, while the “dupp” sound is caused due to the closure of semilunar valves.