The ribcage moves up and out and the diaphragm moves down causing the volume of the chest to increase, resulting in lower pressure so air is drawn in. The opposite happens when exhaling
GasExchange
Oxygen diffuses down its concentration gradient into the capillary bloodstream. Carbondioxide diffuses down its concentration gradient from the blood to the alveoli
Alveoli
Very small and arranged in clusters, creating a large surface area
Capillaries provide a large blood supply, maintaining the concentration gradient
Walls of the alveoli are very thin, meaning there is a short diffusion pathway
