Question

Explain the terms: vital capacity of lungs in terms of IRV (Inspiratory Reserve Volume), ERV (Expiratory Reserve Volume), TV (Tidal Volume) and RV (Residual Volume).

Answer 1

The lungs are the main respiratory organs in humans, which help in the exchange of respiratory gases like oxygen $(O_{2})$ and carbon dioxide $(CO_{2})$. The total lung capacity (TLC) represents the total amount of air-filled in lungs when we inhale with our maximum capacity.

Complete answer:
The maximum volume of air-filled in lungs or total lung capacity can be divided into different component volumes-
Tidal volume (TV) represents the volume of air that is inhaled or exhaled in the normal respiratory cycle. The tidal volume in a normal person is 300-500 ml.
Inspiratory reserve volume (IRV) represents the volume of air that can be forcefully inhaled during a deep breath after filling the lungs with normal tidal volume. The normal value of IRV is 1900-3300 ml in a normal adult.
Expiratory reserve volume (ERV) represents the volume of air that can be forcefully exhaled after the exhalation of normal tidal volume. The normal value of ERV is 700-1200 ml in a normal adult.
The residual volume (RV) is the volume of air that remains inside the lungs after maximum exhalation. The normal value of the residual volume is 1200 ml in a normal adult.

Note: The measurement of different volumes of lungs helps in the measurement of the functioning of the lungs. These measurements are called a pulmonary function test and the instrument used for the measurement of volumes is called Spirometer.