Which volume is considered the total air capacity in the lungs?

Vital capacity is defined as the total amount of air that can be exhaled after a maximal inhalation, and it reflects the maximum volume of air that the lungs can hold for effective breathing. It is the sum of tidal volume, inspiratory reserve volume, and expiratory reserve volume. This measurement is critical in determining the capacity of the lungs to ventilate and the efficiency of gas exchange.

The difference between vital capacity and the other lung volume components is based on their definitions and what they measure. Functional residual capacity, for instance, represents the volume of air remaining in the lungs after a normal expiration, while inspiratory reserve volume and expiratory reserve volume measure the air that can be inhaled or exhaled beyond normal tidal breathing, respectively. Thus, while these other volumes contribute to lung function, they do not encompass the complete air capacity of the lungs as vital capacity does.