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A-Level Biology OCR A

Diffusion Blood Capillaries Area Substances Describe Adapted Function

Capillaries are adapted for their function with a large surface area for diffusion, thin walls (single endothelial cell layer) for a small diffusion distance, and a slower blood flow rate due to their larger total cross-sectional area, allowing more time for exchange.

Capillaries are adapted for their function with a large surface area for diffusion, thin walls (single endothelial cell layer) for a small diffusion distance, and a slower blood flow rate due to their larger total cross-sectional area, allowing more time for exchange.

Front Describe how capillaries are adapted for their function.
Back Adaptations of capillaries:
  • Large surface area for diffusion of substances in/out of blood
  • Walls are single endothelial cell thick - thin layer for diffusion - small diff distance
  • Total cross sectional area of capillaries greater than arteriole so blood flow rate falls - blood moves more slowly giving more time for exchange of substances by diffusion

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