Define vital capacity. What is its significance?
Vital Capacity (VC) is defined as the maximum volume of air a person can breathe in after a forced expiration. It includes the Expiratory Reserve Volume (ERV), Tidal Volume (TV), and Inspiratory Reserve Volume (IRV). Alternatively, it is the maximum volume of air a person can breathe out after a forced inspiration.
The significance of vital capacity lies in its utility for clinical diagnosis. As a pulmonary capacity derived from respiratory volumes, it helps in assessing the functional ability of the lungs to hold and exchange air.
Explanation
The definition is directly sourced from the 'Vital Capacity (VC)' section of the text, which outlines its components (ERV, TV, IRV) and its measurement conditions (forced expiration/inspiration). The significance is derived from the introductory sentence in the context which states that pulmonary capacities 'can be used in clinical diagnosis'.