What components are included in Functional Residual Capacity (FRC)?

Functional Residual Capacity (FRC) refers to the total amount of air remaining in the lungs after a normal exhalation. It is an important measure in assessing lung function and understanding the mechanics of breathing. FRC is composed specifically of two components: Expiratory Reserve Volume (ERV) and Residual Volume (RV).

Expiratory Reserve Volume is the additional air that can be forcibly exhaled after the end of a normal exhalation. Residual Volume is the amount of air that remains in the lungs after a person has exhaled as much as possible and cannot be voluntarily expelled. The combination of these two volumes provides a measure of the functional residual capacity, reflecting the air available for gas exchange and serving as a buffer for maintaining stable oxygen and carbon dioxide levels during the breathing cycle.

The other options include components that do not contribute to FRC. For instance, Tidal Volume (Vt) and Inspiratory Capacity (IC) represent different aspects of lung function and capacity but do not relate directly to the residual air in the lungs. Similarly, Inspiratory Reserve Volume (IRV) is associated with the amount of air that can be inhaled after a normal inhalation and does not play a role in defining F