exchange surfaces

• Specialized exchange surfaces


  Parts of an organism over which they exchange substances with their environment
• Specialized exchange surfaces in humans

  • Alveoli
  • Villi
• Alveoli


  • Small sac-like things found in the lungs at the ends of bronchioles
  • Exchange oxygen and carbon dioxide between air and blood
• Villi


  • Finger-like things found on the inside lining of the small intestines
  • Help absorb nutrients like glucose and amino acids
• Specialized exchange surfaces in plants


  • Root hair cells
  • Leaves
• Root hair cells


  • Help absorb water and mineral ions from the soil
• Leaves


  • Help absorb the carbon dioxide plants need from the air
• Specialized exchange surfaces


  • Large surface area
  • Thin surfaces
  • Permeable to substances being exchanged
  • Good blood supply
  • Good supply of external medium
• Having a large surface area means lots of molecules can diffuse across at the same time, increasing the rate of diffusion
• Having thin surfaces means a short diffusion distance, allowing faster diffusion
• Being permeable allows the substances to diffuse across the surface
• A good blood supply maintains a concentration gradient to allow continued diffusion
• A good supply of the external medium (e.g. air, food) also helps maintain the concentration gradient