Q.Define vital capacity. What is its significance ?

Vital capacity, the maximum air a person can breathe out after breathing in as deeply as possible, is about 3.5–4.8 litres in a healthy adult.

Vital capacity (VC) is defined as the sum of the tidal volume, inspiratory reserve volume, and expiratory reserve volume — in other words, the maximum volume of air that can be expelled from the lungs after a maximal inspiration. It represents the total usable air-exchange capacity of the lungs (excluding the residual volume, which can never be exhaled). In a healthy adult, vital capacity averages about 3,500 to 4,800 mL (roughly 3.5–4 …

Vital capacity - the maximum volume of air that can be forcibly exhaled after the deepest possible inhalation - is approximately 3500-4500 mL, matching option (c).

Vital Capacity (VC) = Tidal Volume (TV) + Inspiratory Reserve Volume (IRV) + Expiratory Reserve Volume (ERV). Since IRV (about 2500-3000 mL) and ERV (about 1000-1100 mL) are added to the TV (about 500 mL), the resulting Vital Capacity in a healthy adult is roughly 3500-4500 mL. …