How do gas laws apply to breathing?

According to Boyle's Law, if a gas's temperature remains constant, its pressure will be inversely proportional to its volume.

When we breathe in, the air inside our lungs takes up more space because our chest expands slightly and the rib cage somewhat expands in size and volume.

Due to the pressure difference that results from this increase in volume, air is forced into our lungs because the pressure inside them is now lower than the pressure outside (in the surrounding atmosphere).

The opposite occurs when you exhale: your lungs and rib cage constrict, resulting in a decrease in volume of air inside them, which raises pressure.

This time, there is an external pressure differential, which causes the air to be forced out!

Gas laws, specifically Boyle's Law and Dalton's Law, apply to breathing by explaining how the volume and pressure of gases in the respiratory system change during inhalation and exhalation. Boyle's Law states that the pressure of a gas is inversely proportional to its volume, so as the volume of the lungs increases during inhalation, the pressure decreases, allowing air to flow into the lungs. Dalton's Law states that the total pressure exerted by a mixture of gases is equal to the sum of the pressures exerted by each gas in the mixture, so the partial pressure of oxygen in the air determines how much oxygen is absorbed into the bloodstream during breathing.