Lub | Dub Sound Heart 'link'

The first sound, the "lub" (medically termed S1), is the deeper and longer of the two tones. It occurs at the beginning of ventricular systole, the phase where the ventricles contract to pump blood out of the heart. When the ventricles contract, the pressure inside them rises rapidly, forcing blood upward toward the atria. To prevent this blood from flowing backward into the atria, the two atrioventricular valves—the tricuspid valve on the right side and the mitral valve on the left—snap shut simultaneously. The abrupt closure of these valves creates the "lub" sound. It is the sound of the heart's "loading" phase concluding and the "firing" phase beginning, propelling blood to the lungs and the rest of the body.

Occurs at the beginning of systole (ventricular contraction). Cause: The closure of the atrioventricular (AV) valves :

The heart has four chambers: two upper atria (right and left) and two lower ventricles (right and left). Blood flows from the atria to the ventricles, then out to the lungs and body. The "lub-dub" corresponds to two distinct phases of the cardiac cycle: lub dub sound heart

As the ventricles contract, pressure inside them rises sharply, forcing the AV valves to snap shut to prevent backflow into the atria. The sudden halting of the valve leaflets and the vibration of the surrounding blood and heart wall produce the lower-pitched, longer "lub" sound.

The "lub-dub" sound is the rhythmic acoustic signature of a living heart, acting as a crucial indicator of cardiovascular health. Far from being the sound of muscle contraction, these noises are the mechanical result of heart valves snapping shut to ensure blood flows in one direction. The Science of "Lub" and "Dub" The first sound, the "lub" (medically termed S1),

The cardiac cycle is divided into two primary phases: (contraction) and diastole (relaxation). Each phase is punctuated by a specific sound, known medically as S1 and S2.

Bilal Hasdemir * The 'lub-dub' sound of a healthy heart is more than just a beat. It's a key to understanding heart health. ... * ... Liv Hospital Heart Murmurs | The Texas Heart Institute® Heart Murmurs. ... Normal heart sounds come in pairs. The sounds are often described as a constant “lub-dub, lub-dub.” The first “... The Texas Heart Institute Heart Murmurs | The Texas Heart Institute® Normal heart sounds come in pairs. The sounds are often described as a constant “lub-dub, lub-dub.” The first “lub-dub” is the sou... The Texas Heart Institute 17.4C: Heart Sounds - Medicine LibreTexts Oct 14, 2025 — To prevent this blood from flowing backward into

The aortic valve closes slightly before the pulmonary valve, especially during inspiration – a phenomenon called physiological splitting .

The cardiac cycle is the sequence of events that occurs with each heartbeat. Here's a step-by-step explanation:

| Feature | S1 ("Lub") | S2 ("Dub") | |---------|------------|------------| | | Start of systole | End of systole / start of diastole | | Valves involved | Mitral & Tricuspid (AV valves) | Aortic & Pulmonary (semilunar valves) | | Pitch | Lower | Higher | | Duration | Slightly longer | Shorter | | Best heard at | Apex of heart (mitral area) | Base of heart (left sternal border) |