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

Transport of oxygen from the atmosphere to tissues and transport of carbon dioxide from tissues to the atmosphere is known as the exchange of gases. This occurs due to the partial pressure of gases, and due to this gases flow from high to low pressure. Partial pressure is the pressure of one gas exerted in a mixture of gases. During inspiration external intercostal muscles contract due to which diaphragm also contracts and changes its shape from normal dome shape to flat. This increases the volume due to which pressure inside the lungs decreases and thus air flows from out to in i.e. inspiration takes place.
During inspiration,

External intercostal muscles contract⏐↓Pulls ribs upwards and outwards⏐↓Diaphragm gets flattened⏐↓Results in increase in volume of thoracic cavity⏐↓Lowers pressure in the lungs than atmospheric pressure⏐↓To fill this gap air from outside rushes into lungs$\begin{array}{c}\text{External intercostal muscles contract}\\ \downarrow \\ \text{Pulls ribs upwards and outwards}\\ \downarrow \\ \text{Diaphragm gets flattened}\\ \downarrow \\ \text{Results in increase in volume of thoracic cavity}\\ \downarrow \\ \text{Lowers pressure in the lungs than atmospheric pressure}\\ \downarrow \\ \text{To fill this gap air from outside rushes into lungs}\end{array}$