Question

The 'lub' sound of the heart is produced due to:

• A. Closing of semilunar valves
• B. Opening of AV valves
• C. Closing of AV valves
• D. Opening of semilunar valves

Hint:

Remember the mnemonic: "Lub-AV, Dub-SL". The 'lub' sound is lower-pitched and lasts longer than the 'dub' sound.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
The characteristic heart sounds ('lub' and 'dub') are mechanical vibrations created when the heart valves close to prevent the backflow of blood.

Step 2: Detailed Explanation:
The heart produces two distinct sounds during each cardiac cycle:
1. First Heart Sound (Lub S1): This sound is created by the closure of the Atrioventricular (AV) valves (the Tricuspid and Mitral valves) at the start of ventricular systole. This closure prevents blood from flowing back into the atria as the ventricles begin to contract.
2. Second Heart Sound (Dub S2): This sound is created by the closure of the Semilunar valves (Aortic and Pulmonary valves) at the beginning of ventricular diastole, preventing blood from flowing back into the ventricles from the arteries.

Step 3: Final Answer:
The 'lub' sound is specifically produced by the closing of the AV valves.