Small intestine

• Has a surface area for absorption of the products of digestion
• Interior of small intestine is covered with millions of villi
• Villi massively increase surface area of small intestine for the absorption of molecules
• Microvilli on the surface of villi increase the surface area even further
• Villi have a very good bloody supply so bloodstream rapidly removes the product of digestion, increases the concentration gradient
• Villi have thin membrane, meaning there’s a short diffusion path
• Any molecules that cannot be be absorbed by diffusion are absorbed by active transport