Anatomy and Physiology II Practice Test

What is the volume included in total lung capacity but not in vital capacity?

1. Residual volume

2. Expiratory reserve volume

3. Tidal volume

4. Inspiratory reserve volume

The correct answer is: Residual volume

Total lung capacity (TLC) encompasses the complete volume of air that the lungs can hold, which includes both the air that can be exhaled and the air that remains in the lungs after a maximum exhalation. Vital capacity (VC), on the other hand, refers specifically to the maximum amount of air that can be exhaled after taking a deep breath, which does not include the air left in the lungs after maximum expiration. Residual volume (RV) is the specific component that contributes to total lung capacity but is excluded from vital capacity. After a forced exhalation, there is always air that remains in the lungs to prevent the alveoli from collapsing. This volume is crucial for sustaining gas exchange between breaths. The other volumes mentioned—expiratory reserve volume, tidal volume, and inspiratory reserve volume—are all included in vital capacity, as they pertain to the air that can be actively inhaled or exhaled during normal and forced breathing maneuvers, but they do not account for the air that remains in the lungs post-exhalation. Thus, residual volume is the only volume that is part of total lung capacity yet not part of vital capacity.