Question:easy
Functional residual capacity is the volume of air in the lungs measured?
Functional residual capacity is the volume of air in the lungs measured?
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FRC is the resting lung volume left at the end of a quiet, passive breath out.
Updated On: Jun 23, 2026
- After normal inspiration
- After normal expiration
- After forceful expiration
- After forceful inspiration
Show Solution
The Correct Option is B
Solution and Explanation
Step 1: Recall the definition by its name: functional residual capacity is the air that functionally stays behind in the lungs during normal breathing.
Step 2: That leftover volume is what you have right after you let a quiet breath out without effort. At this resting point the lung's pull inward and the chest wall's pull outward cancel, setting the relaxed lung volume. It is the sum of expiratory reserve volume and residual volume.
Step 3: So the measuring moment is the end of a normal, passive expiration, which matches the after normal expiration choice.
Step 4: Stopping after a normal inspiration measures a bigger volume, a forced full exhale leaves only residual volume, and a maximal inhale gives total lung capacity. None of these is FRC.
Note: the recall key letter printed for this item points to after normal inspiration, but the standard physiology definition (and the explanation text itself) places FRC at the end of passive expiration, so the medically correct choice is after normal expiration. \[\boxed{\text{After normal expiration}}\]
Step 2: That leftover volume is what you have right after you let a quiet breath out without effort. At this resting point the lung's pull inward and the chest wall's pull outward cancel, setting the relaxed lung volume. It is the sum of expiratory reserve volume and residual volume.
Step 3: So the measuring moment is the end of a normal, passive expiration, which matches the after normal expiration choice.
Step 4: Stopping after a normal inspiration measures a bigger volume, a forced full exhale leaves only residual volume, and a maximal inhale gives total lung capacity. None of these is FRC.
Note: the recall key letter printed for this item points to after normal inspiration, but the standard physiology definition (and the explanation text itself) places FRC at the end of passive expiration, so the medically correct choice is after normal expiration. \[\boxed{\text{After normal expiration}}\]
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