Skip to content When you listen to a heartbeat, the distinctive rhythm isn't the sound of the muscle contracting. Instead, it is the rhythmic snapping of the heart's internal "doors" or valves. The first sound, commonly described as the is known in medicine as S1 . The Mechanics of the "Lub"
It’s the valves hitting each other like cymbals. Instead: what makes the lub sound in the heart
The first sound, the "lub," is scientifically known as S1. This sound marks the beginning of systole, the phase where the heart contracts to pump blood out to the body. To understand the "lub," one must look at the anatomy of the heart’s lower chambers, the ventricles. As these chambers contract, pressure rises rapidly, forcing blood upward toward the exit valves. However, before blood can exit the heart, it must be prevented from flowing backward into the upper chambers, the atria. This is the job of the tricuspid and mitral valves. When the ventricles squeeze, these two valves snap shut simultaneously. The "lub" is the resulting vibration caused by the abrupt halting of blood flow against the closed valve cusps, akin to the sound of a door slamming shut against a strong wind. When you listen to a heartbeat, the distinctive
Want to explore what causes a heart murmur or the “Dub” sound next? Let me know! The Mechanics of the "Lub" It’s the valves
The "lub" sound occurs at the start of , the phase when the heart’s lower chambers (ventricles) begin to contract to pump blood throughout the body. How the Heart Works - How the Heart Beats | NHLBI, NIH
