Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): During normal expiration, air moves out of the lungs because intrapulmonary pressure becomes slightly higher than atmospheric pressure. Reason (R): Relaxation of the diaphragm and external intercostal muscles decreases the thoracic volume, which leads to an increase in intrapulmonary pressure. In t

Step-by-step solution

Assertion (A) is correct because the movement of air into or out of the lungs is driven by pressure gradients. For expiration to occur, the pressure inside the lungs (intrapulmonary pressure) must be higher than the atmospheric pressure, forcing air outward. Reason (R) is also correct and provides the accurate physiological mechanism for this pressure change. Normal expiration is a passive process initiated by the relaxation of the primary inspiratory muscles (the diaphragm and external intercostals). This relaxati