Decrease in thoracic volume is marked by________ A. diaphragm

decrease-in-thoracic-volume-is-marked-by-a-diaphragm

Decrease in thoracic volume is marked by________

A. diaphragm relaxed

B. diaphragm contracted

C. sternum moving towards ventral and anterior direction

D. ribs moving out

This question was addressed to me in an online quiz.

My question is from Mechanism of Breathing-1 in portion Breathing and Exchange of Gases of Biology – Class 11

Correct choice is A. diaphragm relaxed

The explanation: Decrease in thoracic volume is necessary for expiration and is marked by relaxation in diaphragm and external intercostal muscle. Decrease in thoracic volume is necessary in order to build more pressure than atmospheric pressure.