Absorpation in the small intestine

• What is the length of the small intestine?

  around 5m
• The small intestine has a very large surface area for absorption of the products of digestion
• What is in the interior of the small intestine covered in ?

  millions of villi
• Villi massively increases the surface area for the absorption of molecules
• Microcvilli increase the surface area even more
• Villi have very good blood supply so the bloodstream rapidly removes the products of digestion
• What does the thin membrane do ?

  ensures a short diffusion path
• All those features mean that there is a rapid rate of diffusion
• What happens to the molecules that cannot be absorbed by diffusion ?

  they are absorbed by active transport