Adaptations of the Alveoli (Edexcel GCSE Biology): Revision Note

Adaptations of the Alveoli

• The lungs are the gas exchange surface in humans and so are adapted to maximise the exchange of gases by diffusion

• Inside the lungs there are many rounded alveolar sacs, the structure of which aids the process of gas exchange:

  • There are many alveoli, resulting in a large surface area for exchange

  • They are surrounded by a single layer of flattened cells to minimise diffusion distance

  • Ventilation maintains a steep concentration gradient between the alveoli and the blood

    • There are high levels of oxygen and low levels of carbon dioxide in the alveolar air space

  • A good blood supply ensures constant supply of blood high in carbon dioxide and low in oxygen

  • A layer of moisture on the surface of the alveoli helps diffusion as gases dissolve

Alveoli are specifically adapted to maximise gas exchange