Functional residual capacity of lung is defined as:

C i.e. ERV + RV VOLUME Tidal volume 500 m1Q Is the air that moves into the lung (T.V) n,ith each normal inspiration or the volume of air that moves out of lung with each expiration Inspiratory 3300 m1Q The air inspired with a maximal reserve inspiratory effo in excess of tidal volume (IRV) volume Expiratory 1000 inlQ The air expelled with a maximal reserve expiratory effo in excess of tidal volume (ERV) volume Residual 1200 m1Q The amount of air remaining in the Volume (RV) lungs even after forced expiration CAPACITIES Inspiratory capacity I 3800 ml. Total amount of air that can be C=TV+ IRV breathed in. Vital capacity(VC) 4800 ml. Maximal amount of air that can =TV+ IRV+ERV be expelled out force fully after a =IC + ERV maximal (deep) inspiration Functional residual 2200 ml. It is the volume of air remaining capacity in the lung after normal FRC=ERV+RV expiration (after normal tidal expiration) Total lung capacity 6000 ml. The amount of air present in the (TLC) (4.2-6 lung after a maximal inspiration. =TV+IRV+ERV+RV UN) This is the maximum volume to =VC + RV which the lungs can be expandedQ =IC + FRC