role and structure of alveoli walls

• at the end of bronchioles are alveoli which are arranged in clusters in the lungs
• the exchange of oxygen and carbon dioxide takes place in alveoli
• the walls of alveoli are very thin (one cell thick), and each alveoli is surrounded by capillaries through which gases are exchanged
• structure of alveoli like bunches of grapes, increases their surface area to allow maximum crossover, or diffusion, of the two gases back and forth to make process efficient
• diffusion allows the oxygen to move out of alveoli to capillaries and into bloodstream, and the carbon dioxide to move out of capillaries into alveoli and to lungs to be exhaled