Biological Systems MCAT Practice Exam

Which of the following represents the maximum amount of air the lungs can hold?

1. Functional residual capacity

2. Total lung capacity

3. Vital capacity

4. Tidal volume

The correct answer is: Total lung capacity

The total lung capacity is the maximum amount of air that the lungs can hold. It is the sum of all the volumes of air in the lungs, including the tidal volume (the amount of air breathed in and out during normal respiration), the inspiratory reserve volume (the additional air that can be inhaled after a normal inhale), the expiratory reserve volume (the additional air that can be exhaled after a normal exhale), and the residual volume (the air remaining in the lungs after a forceful exhale). This comprehensive measurement reflects the lungs' full capacity for air storage and exchange. In contrast, functional residual capacity refers to the volume of air remaining in the lungs after a normal exhale, vital capacity measures the maximum amount of air that can be exhaled after fully inhaling, and tidal volume is simply the volume of air inhaled or exhaled in a normal breath. Each of these measurements represents a portion of lung function but does not encompass the entire maximum capacity of the lungs. Thus, total lung capacity is the most accurate measure when considering the fullest extent to which the lungs can expand to hold air.