Q. Arrange the given steps of expiration in the sequence of event occurring first I. Relaxation of the diaphragm and sternum II. Reduction of the pulmonary volume III. Expulsion of air from the lungs IV. Increase in intra pulmonary pressure Choose the correct option
A) I $\rightarrow$ II $\rightarrow$ III $\rightarrow$ IV
B) I $\rightarrow$ II $\rightarrow$ IV $\rightarrow$ III
C) IV $\rightarrow$ III $\rightarrow$ II $\rightarrow$ I
D) IV $\rightarrow$ II $\rightarrow$ III $\rightarrow$ I
Explanation
Relaxation of the diaphragm and intercostal muscles returns the diaphragm and sternum to their normal positions and reduces the thoracic volume and thereby the pulmonary volume. This leads to an increase in intra-pulmonary pressure to slightly above the atmospheric pressure, causing the expulsion of air from the lungs, i.e., expiration [image:17_image23.png]
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.