Question

Describe and explain how the structure of the mammalian breathing system enables efficient uptake of oxygen into the blood. ( 4 marks)

Accepted Answer

1. alveoli provide a large surface area;

2. walls of alveoli thin to provide a short diffusion pathway;

3. walls of capillary thin/close to alveoli provides a short diffusion pathway;

4. walls (of capillaries/alveoli) have flattened cells;

5. cell membrane permeable to gases;

6. many blood capillaries provide a large surface area;

7. intercostal/chest muscles/diaphragm muscles / to ventilate lungs / maintain a diffusion/concentration gradient;

8. wide trachea / branching of bronchi/bronchioles for efficient flow of air;

9. cartilage rings keep airways open;

Alveoli Provide Walls Efficient Large Surface Area; Short