Gas exchange

The exchange of gases (O₂ and CO₂) between air and blood occurs in the pulmonary alveoli. The walls of the pulmonary alveoli are very thin and are surrounded by a network of  blood capillaries.

Gas exchange is done through a physical process called diffusion, in which molecules move from where there is more concentration to where there is less until they equalize.

The red blood cells are responsible for transporting oxygen in the blood. Oxygen binds to iron in a protein, called hemoglobin, found in red blood cells, and this is how it is transported. Instead, carbon dioxide is transported dissolved in the blood plasma (the liquid part of the blood).

Animation: Gas exchange in the pulmonary alveoli.

Activity: Name the parts of the respiratory system.

Activity: Where do these actions occur?.

Activity: Path followed by an oxygen molecule in the respiratory system.

Activity: Functions of the parts of the respiratory system.

Gamification: Challenge yourself with these questions about the respiratory system.