Differentiate between the following pairs on the basis of what is mentioned within brackets:
LUBB and DUP (names of the valves whose closure produce the sound)
Topic: Heart sounds
Answer
"LUBB" is produced by the closure of the ATRIOVENTRICULAR valves — the BICUSPID and TRICUSPID valves.
"DUP" is produced by the closure of the SEMILUNAR valves at the roots of the aorta and pulmonary artery.
The brackets ask for the VALVES, so name them — but note the principle behind it, because it eliminates half the wrong answers students give: BOTH SOUNDS ARE MADE BY VALVES CLOSING, never opening.
The order makes sense if you follow the blood: the valves close in the same sequence the blood travels — first those between atrium and ventricle (LUBB), then those at the exits into the arteries (DUP).
THE MEDICAL RELEVANCE: a "MURMUR" means a valve is leaking or not closing properly, so a doctor listening to the chest with a stethoscope is checking the valves.
| Point of difference | LUBB | DUP |
|---|---|---|
| Valves closing | Bicuspid and tricuspid (atrioventricular) | Semilunar (aortic and pulmonary) |
| When | At the start of ventricular SYSTOLE | At the start of ventricular DIASTOLE |
| Character | Longer and duller | Short and sharp |