The second heart sound 'dup' is heard due to? & x20; - RUHS, Jaipur, M.Sc Nursing Entrance Exam-2019

RUHS, Jaipur, M.Sc Nursing Entrance Exam-2019

Applied Physiology

Easy

Appeared in: RUHS, Jaipur, M.Sc Nursing Entrance Exam-2019

Explanation

The second heart sound (S2), described as 'dup' or 'dub', is generated by the closure of the semilunar valves.
The semilunar valves consist of the aortic valve (on the left side of the heart) and the pulmonary valve (on the right side).
This closure event occurs at the end of ventricular systole (contraction) and marks the beginning of diastole (relaxation).
As the ventricles relax, the pressure within them drops below the pressure in the aorta and pulmonary artery, causing the blood to attempt to flow backward, which snaps the semilunar valves shut.

Option A: This is incorrect. The opening of the aortic and pulmonary valves is a passive event that is normally silent and does not produce the 'dup' sound.
Option B: This is a duplicate of the first option and is also incorrect. Valve opening is a silent event in a healthy heart.
Option C: This is incorrect. The opening of the atrioventricular (mitral and tricuspid) valves is also a silent event. Their closure, not opening, produces the first heart sound (S1 or 'lub').

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Physiology of Heart Sounds as background academic context rather than a clinical decision trigger.
Auscultation of heart sounds is a fundamental nursing assessment skill used to detect cardiac abnormalities.
Changes in the S2 sound can indicate underlying pathology. For example, a loud pulmonary component of S2 (P2) can suggest pulmonary hypertension. A 'fixed split' S2 (where the split does not vary with respiration) is a classic sign of an Atrial Septal Defect (ASD).
What if? If a patient has severe aortic stenosis, the aortic valve closure (A2 component of S2) may become very soft or inaudible. The nurse might only hear the pulmonary valve closure (P2), resulting in a 'single' S2 sound.

How to Approach the Question

First, identify the key term in the question: 'second heart sound' and its descriptor 'dup'.
Recall the two primary, normal heart sounds: S1 ('lub') and S2 ('dup').
Associate each sound with the mechanical event that causes it. Remember the mnemonic 'LUB' is S1, 'DUB' is S2.
Recall that heart sounds are produced by the closure of valves, not their opening. Opening is a silent event in a healthy heart.
S1 ('lub') is caused by the closure of the atrioventricular (AV) valves (mitral and tricuspid).
S2 ('dup') is caused by the closure of the semilunar (SL) valves (aortic and pulmonary).

Concept Tested & Keywords

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