Small intestine

• Food molecules move


  1. From the small intestine

  2. Into the blood
• Food molecules move


  • From an area of high concentration
  • To an area of low concentration
• Adaptations of the small intestine


  • The small intestine is very long
  • The inner lining is folded into finger-like projections called villi
  • Villi are covered in even smaller structures called microvilli
  • This increases the surface area for absorption of nutrients
• Villi


  • The walls are very thin, only the width of one cell
  • This means diffusion of nutrients into the blood is quicker
• Villi


  • Each villus has a good blood supply provided by capillaries
  • The blood quickly carries away absorbed food
  • This creates a high concentration gradient between the intestine and the blood
• Absorption of simple food molecules


  Over the surface of the gut wall
• Digested lipids


  1. Pass through the epithelium

  2. Into a lacteal
• Lacteals


  • Their job is to transport away fatty acids when fats are broken down
• Epithelial cells


  • Have projections that increase the surface area for absorption