Which heart sound is associated with the closure of the atrioventricular valves?

The heart sound associated with the closure of the atrioventricular valves is the first heart sound, known as S1. This sound occurs at the beginning of ventricular contraction, or systole, when the mitral and tricuspid valves close to prevent the backflow of blood from the ventricles into the atria. This closure is critical for maintaining one-way blood flow through the heart and is a key moment in the cardiac cycle.

S1 is typically described as a "lub" sound, and it marks the transition from diastole, when the heart chambers fill with blood, to systole, when the ventricles contract and pump blood to the lungs and the rest of the body. Understanding the significance of S1 in the normal cardiac cycle is essential for assessing heart function and identifying potential abnormalities.