Understanding Heart Sounds and the Cardiac Cycle

The heart works in cycles, and each part of this cycle creates sounds that tell us how it’s doing. Let’s break it down in simple terms:

1. Systole (When the Heart Beats):

   • During this phase, the heart's lower chambers, called ventricles, squeeze tightly.
   • This squeezing pumps blood out of the heart.
   • As the ventricles contract, special doors called atrioventricular (AV) valves close.
   • This closing makes the first sound of the heartbeat, which we often call "lub."
   • At the same time, the pressure builds up in the arteries, causing other doors called semilunar valves to open. This lets blood flow out of the heart.

2. Diastole (When the Heart Rest):

   • In this phase, the heart relaxes after the beat.
   • The semilunar valves close, which makes the second sound we hear, known as "dub."
   • This closing means that the squeezing part is done, and the heart starts to fill up with blood again.

So, when we listen to these sounds, they give us important clues about how well the heart is working during its cycle!