Small Intestine

• What is the primary function of the small intestine?

  To absorb the products of digestion
• How are large food molecules broken down during digestion?

  By enzymes into smaller molecules
• What 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?

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

  Villi
• How do villi contribute to absorption?

  They massively increase the surface area
• What are microvilli?

  Small projections on villi
• How do microvilli affect absorption?

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

  It rapidly removes products of digestion
• What effect does a good blood supply have on concentration gradient?

  It increases the concentration gradient
• What feature of villi ensures a short diffusion path?

  A thin membrane under the villi
• What is the result of the adaptations of the small intestine?

  A rapid rate of diffusion into the bloodstream
• How are molecules that cannot be absorbed by diffusion taken up?

  By active transport
• What are the adaptations of the small intestine for absorption?

  • Long length (around 5 meters)
  • Presence of villi to increase surface area
  • Microvilli on villi for further surface area increase
  • Good blood supply to remove digestion products
  • Thin membrane for short diffusion path
  • Active transport for non-diffusible molecules