Absorption in the small intestine

• What happens to large food molecules during digestion?

  They are broken down into smaller molecules by enzymes
• Which enzyme digests starch into simple sugars?

  Amylase
• Where are the products of digestion absorbed?

  In the small intestine
• How long is the human small intestine?

  Around 5 meters
• Why is the length of the small intestine important for absorption?

  It provides a very large surface area for absorption
• What structures cover the interior of the small intestine to aid absorption?

  Millions of villi
• How do villi contribute to the absorption process?

  They massively increase the surface area for absorption
• What are microvilli and how do they assist in absorption?

  Microvilli increase the surface area even further on the villi
• Why is a good blood supply important for the villi?

  It rapidly removes the products of digestion, increasing the concentration gradient
• What role does the thin membrane under the villi play?

  It ensures a short diffusion path for absorption
• How do the adaptations of the small intestine facilitate the absorption of digestion products?

  They increase surface area, improve blood supply, and shorten diffusion paths
• What happens to molecules that cannot be absorbed by diffusion in the small intestine?

  They are absorbed by active transport
• What are the key adaptations of the small intestine for absorbing the products of digestion?

  • Long length (around 5 meters) increases surface area
  • Millions of villi increase surface area for absorption
  • Microvilli on villi further increase surface area
  • Good blood supply enhances concentration gradient
  • Thin membrane under villi shortens diffusion path
  • Active transport for molecules that cannot diffuse