Inspiratory reserve volume is the volume of air which can be inspired in addition to the normal inspiration.

Answer

### Step-by-Step Solution:

1. **Definition of Inspiratory Reserve Volume (IRV)**:
- Inspiratory Reserve Volume is defined as the additional volume of air that can be inhaled after a normal inspiration. It represents the extra air that can be drawn into the lungs beyond the tidal volume during deep or forceful breathing.

2. **Understanding Tidal Volume**:
- Tidal Volume is the amount of air inhaled or exhaled during normal breathing. It is the baseline volume of air exchanged with each breath.

3. **Relation Between IRV and Tidal Volume**:
- Inspiratory Reserve Volume is the volume of air that can be inhaled after the normal tidal volume. Therefore, IRV = Total Lung Capacity - (Tidal Volume + Expiratory Reserve Volume + Residual Volume).

4. **Quantitative Values**:
- The average Inspiratory Reserve Volume varies between genders. For males, it is approximately 3000 ml, while for females, it is about 2100 ml. This indicates that males generally have a higher lung capacity for additional air intake compared to females.

5. **Significance of IRV**:
- Understanding IRV is crucial for assessing lung function and respiratory health. It helps in determining the capacity of the lungs to take in additional air, which is important during physical exertion or in respiratory conditions.