3.1.1 Exchange surfaces - Specialised exchange surfaces

Question 1

What are the features of an effective exchange surface?

Answer 1

• Increased surface area, e.g. root hair cells in plants and the villi in the small intestine of mammals.
• thin layers / short diffusion path, e.g. alveoli in the lungs and the villi of the small intestine.
• good blood supply (steep concentration gradient), e.g. alveoli in the lungs, the gills of a fish and the villi of the small intestine.
• ventilation to maintain diffusion gradient, e.g. the alveoli and the gills of a fish.