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 → II → III → IV        b)    I → II → IV → III    c) IV → III → II → I       d) IV → II → III → I

AA
BB
CC
DD

A.

(b) 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

 



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