Absorption in the Small Intestine

• The human small intestine has a length of around 5m, providing a very large surface area for absorption of the products of digestion.
• The interior of the small intestine is covered with millions of villi. These increase the surface area for the absorption of molecules. Microvilli on the surface increase the surface area even further.
• Villi have a very good blood supply so the bloodstream rapidly removes the products of digestion, increasing the concentration gradient
• The thin membrane of the villi ensures a short diffusion path, meaning there is a rapid rate of diffusion. If diffusion is not possible then active transport is used instead