What Produces The Lub Dub Heart Sounds [top] | Direct

To stop this backflow, the (pulmonary and aortic) snap shut. Unlike the fleshy AV valves, these look like three tiny crescent moons (hence "semilunar") shaped like a Mercedes-Benz logo.

But the truth is far stranger and more fascinating. The "Lub-Dub" isn't the sound of muscle flexing. It’s not blood rushing through pipes. And it’s definitely not the heart "pumping."

The "Dub" is the sound of the escape hatches closing after the blood has left. Part 4: The Bizarre Physics of the Silent Gap Notice the rhythm: Lub...Dub...pause...Lub...Dub...pause. what produces the lub dub heart sounds

For most of us, it’s the most reliable metronome we’ll ever own. We call it a heartbeat, but in medical terms, it’s known as the . It’s so familiar that we rarely question it. We assume the sound is simply the heart contracting like a fist squeezing blood.

But sound needs vibration, and muscle contraction is a relatively smooth, slow process. It generates almost no audible noise. If you could stand inside a healthy heart during a beat, you wouldn’t hear a "crunch" or a "squeeze." You’d hear... silence, followed by chaos. To stop this backflow, the (pulmonary and aortic) snap shut

In fact, your heart is mostly silent during the actual pump.

As the ventricles finish squeezing, the pressure inside them drops rapidly. The blood that was just blasted into the arteries (the lungs and body) suddenly wants to rush backward into the heart. It’s like a wave hitting a seawall. The "Lub-Dub" isn't the sound of muscle flexing

The "Lub" is the sound of the exit doors closing just as the heart tries to pump. Part 3: The "Dub" (The Escape Hatch Snap) After the "Lub," the ventricles continue to squeeze. They blast blood out through two other doors: the pulmonary valve (to the lungs) and the aortic valve (to the body). For a brief moment, the heart is emptying.