Topics:
Animal Physiology, Animal Refresher
Second Heart Sound (Dub) Production
The second heart sound (dub / diastolic sound) is produced by:
- Closure of A-V valves
- Opening of A-V valves
- Closure of semilunar valves — Correct Answer
- Opening of semilunar valves
Explanation:
Correct Answer: Closure of semilunar valves
The second heart sound (S2 / 'dub' / diastolic sound) is produced by the closure of the semilunar valves — aortic valve and pulmonary valve — at the beginning of ventricular diastole (when ventricular systole ends).
Heart Sound Summary
| Sound | Cause | Timing |
|---|---|---|
| S1 (Lub) | Closure of A-V valves (mitral + tricuspid) | Start of systole |
| S2 (Dub) | Closure of semilunar valves (aortic + pulmonary) | Start of diastole |
Murmurs
Heart murmurs occur when blood flows turbulently through valves. A systolic murmur between S1 and S2 suggests aortic stenosis or mitral regurgitation. A diastolic murmur between S2 and next S1 suggests aortic regurgitation or mitral stenosis.
📚 About this Topic — Animal Physiology
This multiple choice question is from Animal Physiology, Animal Refresher. It has 4 options with a detailed explanation of the correct answer. Practice more MCQs from Animal Physiology to strengthen your preparation.
