Most of us think it’s the sound of our heart beating or contracting, but it’s not.

What we’re hearing is the sound of two pairs of valves closing inside the chambers of our heart.

Can’t quite picture it? 

Picture it like the gates at a bustling airport, allowing passengers to move forward while preventing any backward flow.

Imagine navigating two security lines: one for travelers heading to exciting destinations and another for those returning home. Each line has two sets of gates, much like turnstiles, controlling the flow of passengers in a unidirectional motion.

As the first set of gates opens simultaneously for both lines, regulating the influx of travelers into the terminal, it produces a distinct sound - click.

Now, envision the travelers from different lines progressing to the next set of gates for security screening. As these globetrotters pass through the second set, the gates synchronize and create a different sound - clack.

Throughout the day, passengers in both lines move through these two sets of gates simultaneously - click-clack, click-clack, click-clack.

Anyone who attempts to backtrack is out of luck; these gates only permit forward progression.

This airport scenario, minus the long security lines and the duty-free temptation, mirrors the intricate workings of the valves in your heart.

Whether a red blood cell is on its way to the lungs or arteries leading to the rest of the body, it must navigate through two distinct chambers and sets of valves before propelling out of the heart toward its destination.

With such a dynamic process, it’s fascinating that the sound of your heart doesn’t keep you up at night.

Instead, after a day of travel, as you remove your passport and settle into bed, you faintly hear the rhythmic movement of those four gates – the valves – working in tandem.

Click-clack. Click-clack. Click-clack.

And in your heart, it’s lub-dub.

Lub-dub. Lub-dub.