AQA GCSE Biology · 8461
Specification 4.1.3.1, 4.2.2.2 · Paper 1
A tiny air sac in a mammal's lung where oxygen and carbon dioxide are exchanged with the blood.
Revise: Adaptations of Exchange Surfaces in Plants and AnimalsEach alveolus has a thin wall and is surrounded by capillaries, giving oxygen a short route into the blood and carbon dioxide a short route out. Breathing moves fresh air in and used air out; blood flow and ventilation together maintain the concentration differences for gas exchange.
- Revise: The Heart, Double Circulation and the Pacemaker
A tiny air sac in the lungs where oxygen enters the blood and carbon dioxide leaves it.