Digestive system

• Two main roles of the digestive system

  Digestion

  Absorption
• Digestion

  Process of breaking down large food molecules into smaller molecules
• Absorption

  Process of absorbing these small food molecules into the body
• Why do we chew food

  Break it down into smaller pieces.
• What’s the purpose of breaking food down?

  Increases the surface area for enzymes to act on

  Makes the food easier to swallow
• Mouth —> Oesophagus —> Stomach —> Small intestine —> Large intestine —> Rectum —> Anus
• 3 things the stomach does to aid digestion

  Contracts it’s muscular walls to churn and mix the food

  Produces pepsin that breaks proteins down into amino acids

  Produces hydrochloric acid which provides the right pH for pepsin and kills microorganisms
• Bile

  Made in the liver but stored in the gall bladder
• Roles of bile

  Emulsify lipids

  Neutralise acid from the stomach
• Role of salivary glands

  Moistens food making it easier to swallow

  Contains salivary amylase which digests starch to maltose
• Which enzymes does the pancreas produce

  Carbohydrates

  Proteases

  Lipases
• What enzyme does the stomach produce

  Proteases (e.g pepsin)
• What enzyme does the small intestine produces

  Carbohydrases (e.g amylase)

  Proteases

  Lipases
• Two roles of the small intestines

  Where most digestion takes place

  Where nutrients are absorbed
• Main role of large intestines

  Reabsorb water
• Main role of the rectum

  To store faeces until they’re ready to be released
• Four ways in which villi are adapted to their role

  Lots of them therefore giving them a large surface area

  Walls only have a single layer of cells - nutrients only have to diffuse a short distance

  Have a good supply of blood

  Cells lining the villi have microvilli on their surface