A-Level Biology OCR A
Alveoli Air Surface Elastic Structure Makes Epithelial Fibres
| Front |
Describe the structure of alveoli & explain how its structure makes it adapted for its function |
| Back |
Alveoli:- Tiny air sacs - main gas exchange surface of body
- Consist of flattened epithelial cells, collagen and elastic fibres (elastin)
- Elastic fibres - allow alveoli to stretch when air is drawn in, when they return to their resting size they help squeeze air out - elastic recoil of lungs
- Large surface area - high rate of diffusion
- Thin layers - alveoli and capillaries surrounding are 1 epithelial cell thick
- Good blood supply - surrounded by a lot of capillaries - constant flow of blood brings CO2 and carries O off maintaining steep conc gradient
- Good ventilation - breathing moves air in/out maintaining steep gradient for both diffusions
- Lung surfactant - thin solution layer the inner surface is covered with that makes it possible for alveoli to remain inflated
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A-Level Biology OCR A