Question

The capacity of lungs for air in a healthy man is
A. 500 ml
B. 1000 ml
C. 1500 ml
D. 3000 ml
E. 6000 ml

Answer 1

In a healthy man, the capacity of lungs for air when they are inflated fully is known as the total lung
capacity (TLC) which is equal to the sum of tidal volume (TV), expiratory reserve volume (ERV),
inspiratory reserve volume (IRV), and residual volume (RV).

Complete answer:
Option (A) is incorrect. 500 ml volume represents the tidal volume of the lungs in a healthy man. The tidal volume of lungs can be defined as the amount of air moving in or out of the lungs during each respiratory cycle.
Option (B) is incorrect. 1000 ml volume represents the expiratory reserve volume of lungs in a healthy man. It is the volume of air that can be exhaled forcefully after a normal resting expiration.
Option (C) is incorrect. 1500 ml volume represents the residual volume of lungs in a healthy man. It can
be defined as the volume of air remaining inside the lungs even after forceful expiration.
Option (D) is incorrect. 3000 ml volume represents the inspiratory reserve volume of lungs in a healthy
man. It can be defined as the volume of air that can be inhaled after a normal process of inspiration.
Option (E) is correct. 6000 ml volume represents the total lung capacity of lungs in a healthy man. It can
be calculated by adding the four volumes of lungs i.e., TV, IRV, ERV, and RV.
$\Rightarrow {\rm{TLC }} = {\rm{ TV}} + {\rm{IRV}} + {\rm{ERV}} + {\rm{RV}}$
Since TV is 500 ml, IRV is 3000 ml, ERV is 1000 ml, and RV is 1500 ml; therefore,
$\Rightarrow {\rm{TLC }} = {\rm{ }}500 + 3000 + 1000 + 1500$ml
$\Rightarrow {\rm{TLC }} = {\rm{ 6000}}$ml

Hence, the correct option is (E).

Note:
The lung volumes such as tidal volume, expiratory reserve volume, and inspiratory reserve volume can
be measured by spirometry while the residual volume of lungs and the total lung capacity of lungs can
be measured directly by plethysmography, nitrogen washout, and helium dilution technique. Thus, the
total lung capacity of lungs in a healthy man is about 6000 ml or 6 L