Correct Option
The correct option is
A is true but R is false
.Explanation
In human physiology, Residual Volume (RV) refers to the volume of air remaining in the lungs even after a forcible expiration. This volume ensures that the lungs do not collapse and that gas exchange continues uninterrupted between breathing cycles.
Statement-wise Analysis
- Assertion (A): Correct. The lungs always retain a certain amount of air (Residual Volume) to ensure that the alveoli do not collapse. This retained air allows for the continuous diffusion of oxygen into the blood and carbon dioxide out of the blood, even during the exhalation phase when no fresh air is being inhaled. Without this, gas exchange would be intermittent.
- Reason (R): Incorrect. The presence of residual volume specifically means that the lungs do not completely empty of air or carbon dioxide during exhalation. If the lungs were to empty completely, the alveoli would collapse (atelectasis), making re-inflation difficult and halting gas exchange. Furthermore, the air in the lungs is always a mixture of fresh air and residual air; it is never completely cleared of carbon dioxide in a single cycle.
Key Takeaway
Residual Volume prevents alveolar collapse and buffers the concentration of respiratory gases, ensuring continuous gas exchange. The lungs never completely empty of air or carbon dioxide during a respiratory cycle.