BRAINCAKEGas Exchange in the Alveoli
Gas exchange in the lungs takes place across the walls of the alveoli. Each alveolus is surrounded by a dense network of blood capillaries.
Oxygen diffuses from the air in the alveolus into the blood. Air in the alveoli has a high concentration of oxygen, while blood arriving from the pulmonary artery is deoxygenated, so it has a lower oxygen concentration than the alveolar air. Oxygen crosses:
1. the thin layer of moisture lining the alveolus, where it dissolves;
2. the alveolar epithelium (one cell thick);
3. the capillary endothelium (one cell thick);
4. the plasma, into the red blood cells, where it binds to haemoglobin to form oxyhaemoglobin.
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More in Gas Exchange
- Gas Exchange in Large Organisms
- Factors Affecting the Rate of Diffusion
- Effective Gas Exchange Systems
- The Human Gas Exchange System
- Adaptations of the Human Gas Exchange System
- Breathing
- Inhalation
- Exhalation
All 23 lessons in Gas Exchange · All Edexcel AS-level Biology topics