Absorption of Materials

• Absorption surfaces


  • Large surface area to maximise absorption
  • Thin walls to absorb materials easily and quickly
  • Large blood supply to increase carrying of materials to different locations e.g. cells or lungs
• Thin wall


  One cell thick
• Lungs


  • Large number of alveoli (air sacs) to give a large surface area
  • Thin walls to allow gases to be exchanged with the blood
• Oxygen moves from a high concentration in the lungs


  To a low concentration in the blood
• Carbon dioxide moves from a high concentration in the blood


  To a low concentration in the lungs where it can be removed from the body
• Small intestine


  • Large number of villi to increase the surface area for absorption
  • Thin walls to aid the absorption of dissolved nutrients
• Nutrients absorbed in the small intestine

  • Glucose
  • Amino acids
  • Fatty acids
  • Glycerol
• Absorption locations in the small intestine

  • Blood capillaries
  • Lacteals
• The thin wall of the villus is one cell thick to increase the speed of absorption
• The blood capillary absorbs amino acids and glucose
• The lacteal absorbs fatty acids and glycerol