Normal expiratory reserve volume of adult-
**Core Concept**
Normal expiratory reserve volume (ERV) is the additional volume of air that can be forcibly exhaled from the lungs after a normal exhalation. It is an important component of lung function and is used to assess respiratory health.
**Why the Correct Answer is Right**
The normal ERV is approximately 1200-1500 mL in adult males and 900-1200 mL in adult females. This value can vary depending on factors such as age, sex, height, and weight. The ERV is measured during a spirometry test, which involves taking a deep breath in and then exhaling as much air as possible, followed by a forced exhalation. The ERV is the difference between the total lung capacity (TLC) and the forced expiratory volume (FEV) at the end of the first second (FEV1).
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because ERV is not the same as tidal volume (TV), which is the normal volume of air inhaled or exhaled during quiet breathing.
**Option B:** This option is incorrect because residual volume (RV) is the volume of air remaining in the lungs after a maximal exhalation, not the ERV.
**Option C:** This option is incorrect because inspiratory capacity (IC) is the maximum volume of air that can be inhaled after a normal exhalation, not the ERV.
**Clinical Pearl / High-Yield Fact**
The ratio of ERV to TLC is an important indicator of lung function and can be used to diagnose conditions such as chronic obstructive pulmonary disease (COPD).
**Correct Answer: D. 1200-1500 mL.**