Sound — What Makes The Lub Dub
The first part of the heartbeat, known medically as S1, is the "lub." This sound marks the beginning of systole, which is the phase where the heart contracts to pump blood out to the body.
The first part of the heartbeat, known medically as S1, is the "lub." This sound marks the beginning of systole, which is the phase where the heart contracts to pump blood out to the body.