During which mechanical event of the cardiac cycle is the second heart sound produced?

During which mechanical event of the cardiac cycle is the second heart sound produced?

• A. Closing of the atrioventricular valves
• B. Closing of the semilunar valves
• C. Atrial contraction
• D. Ventricular filling

Answer: (B)

The second heart sound, commonly referred to as "S2," occurs during the closing of the semilunar valves. This sound is produced when the aortic and pulmonary valves snap shut at the end of ventricular systole, signaling the transition from ventricular contraction to ventricular diastole. This event is crucial in the cardiac cycle as it helps to prevent the backflow of blood into the ventricles from the aorta and pulmonary artery. Understanding this sound is important because it provides insights into the mechanical function of the heart and its efficiency in blood circulation. The closure of the semilunar valves occurs after the blood has been ejected from the ventricles into the great vessels, marking the completion of one phase of the cardiac cycle and the beginning of another. This transition is critical for maintaining proper blood flow and pressure within the circulatory system.

The second heart sound, commonly referred to as "S2," occurs during the closing of the semilunar valves. This sound is produced when the aortic and pulmonary valves snap shut at the end of ventricular systole, signaling the transition from ventricular contraction to ventricular diastole. This event is crucial in the cardiac cycle as it helps to prevent the backflow of blood into the ventricles from the aorta and pulmonary artery.

Understanding this sound is important because it provides insights into the mechanical function of the heart and its efficiency in blood circulation. The closure of the semilunar valves occurs after the blood has been ejected from the ventricles into the great vessels, marking the completion of one phase of the cardiac cycle and the beginning of another. This transition is critical for maintaining proper blood flow and pressure within the circulatory system.