(a) IRV and ERV:-
Inspiratory reserve volume (IRV):-
It is the maximum volume of air that can be inhaled after a normal inspiration. 2. It is about 2500 – 3500 mL in the human lungs.
Expiratory reserve volume (ERV):-
It is the maximum volume of air that can be exhaled after a normal expiration. 2. It is about 1000 – 1100 mL in the human lungs.

(b) Inspiratory capacity and Expiratory capacity:-
Inspiratory capacity (IC):-
1. It is the volume of air that can be inhaled after a normal expiration.
2. It includes tidal volume and inspiratory reserve volume. IC = TV + IRV
Expiratory capacity (EC):-
1. It is the volume of air that can be exhaled after a normal inspiration.
2. It includes tidal volume and expiratory reserve volume. EC = TV + ERV

(c) Vital capacity and Total lung capacity
Vital capacity (VC):-
1. It is the maximum volume of air that can be exhaled after a maximum inspiration. It includes IC and ERV.
2. It is about 4000 mL in the human lungs.
Total lung capacity (TLC):-
1. It is the volume of air in the lungs after maximum inspiration. It includes IC, ERV, and residual volume.
2. It is about 5000 – 6000 mL in the human lungs.

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