2.7 - Digestive System

• What are the roles of the digestive system?

  Digestion - process of breaking down large food molecules into smaller molecules

  Absorption - process of absorbing these small molecules into the body
• When we chew food, our teeth physically break the food down into smaller pieces. How does this help?

  It makes the food easier to swallow

  It increases the surface area for enzymes to act on
• What do the salivary glands do?

  Release saliva which lubricates the food and makes it easier to swallow. Contains amylase which breaks down starch into glucose
• What is the name for the tube that carries food from the mouth to the stomach?

  Oesophagus
• What are the roles of the stomach?

  1. Contracts its muscular walls to churn and mix food.
  2. Produces pepsin, a protease enzyme, and breaks down proteins into amino acids.
  3. Produces hydrochloric acid which provides the pH for pepsin to function and kills microorganism.
• What are the roles of bile?

  Made by liver, stored in gallbladder.

  After a meal it is released into small intestine:

  • Emulsifies lipids
  • Neutralises acid from the stomach
• Which enzymes does the pancreas produce?

  Amylase

  Protease

  Lipase
• Which enzymes does the small intestine produce?

  Amylase

  Protease

  Lipase
• What are villi?


  Small finger-like projections in the small intestine that absorb nutrients.
• How are villi adapted to their role?

  Lots of them - large surface area

  Single layer of cells - nutrients don’t have to diffuse very far

  Good blood supply - maintains strong concentration gradient between lumen and blood

  Cells lining villi have microvilli on their surface - increased surface area
• What is the main role of the large intestine?

  Absorb water