Zoology - Breathing and Exchange of Gases Question with Solution | TestHub

Mechanism

$\mathrm{A}.$Contraction of diaphragm$\to$Volume of the thoracic chamber in the antero-posterior axis increases.

$\mathrm{B}.$Contraction of external intercostal muscles$\to$Ribs and the sternum are lifted up$\to$Increase in the volume of the thoracic chamber in the dorso-ventral axis.

$\mathrm{C}.$Increase in the thoracic volume$\to$Increase in pulmonary volume$\to$Decrease in the intra-pulmonary pressure.

$\mathrm{D}.$Intra-pulmonary pressure becomes less than the atmospheric pressure. This forces the air from outside to move into the lungs (inspiration).