"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).
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
A slightly lower-pitched, longer "lub."
"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). "The squeeze is over