Lub-dub Sounds — [top]

Spoiler alert: It’s not the heart muscle contracting, and it’s not the blood whooshing around.

Think of your heart as a house with four rooms (chambers) and four doors (valves). To get blood moving in the right direction, those doors must open to let blood through and then slam shut to prevent it from leaking backward. The "lub" and "dub" are the sonic booms of those doors closing. The first sound, "Lub" (clinically known as S1 ), marks the beginning of systole —the moment your heart squeezes blood out to the body. lub-dub sounds

"The squeeze is over. We are locking the exit doors to keep blood moving forward." The Silence in Between Have you noticed the pause between the "lub" and the "dub"? That silence is the systolic pause (the squeeze). The longer pause after the "dub" is the diastolic pause (the rest/fill). Spoiler alert: It’s not the heart muscle contracting,

The powerful lower chambers of your heart (the ventricles) begin to contract. This sudden spike in pressure slams shut the two top valves: the Mitral and Tricuspid valves. These valves separate the upper chambers (atria) from the lower chambers. When they close, they vibrate, creating that thudding "lub" sound. The "lub" and "dub" are the sonic booms

After the heart squeezes blood out to the lungs and body, the ventricles relax. The blood in the major arteries (the Aorta and Pulmonary Artery) wants to rush back into the heart, but two different valves—the Aortic and Pulmonary valves—snap shut to stop it. Their closure creates the "dub."

"The squeeze is starting. No blood is allowed back into the top rooms." Breaking Down the "Dub" (S2) The second sound, "Dub" (clinically known as S2 ), marks the end of systole and the beginning of rest (diastole).