Describe and explain how the human lungs are adapted for efficient gas exchange (3 marks)
- There are millions of alveoli (gas exchange surface), so they have a very large surface area collectively, which is further increased by having a folded membrane. A larger surface areas means there is a faster rate of diffusion of oxygen and carbon dioxide.
2) Alveoli walls only have a single layer of epithelial cells. The walls of capillaries surrounding the alveoli only have a single layer of endothelial cells. Therefore, there is a shorter diffusion pathway, so there is a faster rate of diffusion of oxygen and carbon dioxide.
3) Ventilation of the lungs brings oxygen into the alveoli and removes carbon dioxide. The circulation of blood through capillaries is constantly bringing in blood with low oxygen. This maintains a steep concentration gradient across the alveolar wall for a faster rate of diffusion for oxygen and carbon dioxide.
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