At this moment, the heart's ventricles (the strong, lower pumping chambers) contract. They squeeze to push blood upward. To prevent that blood from leaking backward into the upper chambers (the atria), two flaps called the slam shut.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional for concerns regarding your heart health.

You’ve heard the phrase "lub dub" in movies and doctor’s offices, but what does it actually mean? We break down the science behind the heartbeat sound and why it matters. Have you ever been sitting in a quiet room, resting your head on a pillow, and suddenly heard your own heart beating? Lub-dub. Lub-dub. Lub-dub.