Lub Dub Heart — Sounds ^hot^

During , intrathoracic pressure decreases. This creates a suction effect that increases venous return to the right side of the heart. Consequently, the right ventricle takes longer to empty, delaying the closure of the pulmonic valve (P2). Simultaneously, increased capacity in the pulmonary vessels decreases return to the left heart, causing the aortic valve (A2) to close slightly earlier.

: It is primarily produced by the simultaneous closure of the mitral and tricuspid (atrioventricular) valves . lub dub heart sounds

The classic "lub-dub" isn't actually the sound of your heart muscle squeezing; it’s the sound of your , much like a door slamming. These sounds, known medically as S1 (lub) and S2 (dub), mark the major mechanical transitions in your cardiac cycle. The "Lub-Dub" Breakdown Medical Term What it Signals Lub S1 Closure of Mitral and Tricuspid valves During , intrathoracic pressure decreases

| Feature | | S2 ("Dub") | | :--- | :--- | :--- | | When it occurs | Beginning of systole (ventricular contraction) | Beginning of diastole (ventricular relaxation) | | Which valves close? | Atrioventricular (AV) valves (Mitral & Tricuspid) | Semilunar (SL) valves (Aortic & Pulmonic) | | Location of sound | Loudest at apex of heart (5th intercostal space, midclavicular line) | Loudest at base of heart (2nd intercostal space, right & left sternal border) | | Pitch | Slightly lower, longer | Slightly higher, shorter | | Timing relative to pulse | Occurs just before the carotid pulse | Occurs just after the carotid pulse | These sounds, known medically as S1 (lub) and