Digestive System

Digestive System

Mouth
1. adds saliva, breaks food into small pieces
2. Oesophagus
  1. squeezes food towards stomach, connects mouth and stomach
  2. Stomach
    1. Churns food up with acid, adds protein-digesting enzymes
    2. Small intestine
      1. contains digestive enzymes made by the pancreas, allows nutrients to pass through the walls into the blood
      2. Pancreas
        makes digestive enzymes, secretes enzymes into small intestine
        Large intestine
        water passes through it's walls into the blood, undigested food passes along this tube
        Liver
        makes bile, processes nutrients
        Gall bladder
        releases bile into small intestine when needed, stored bile made by liver
Chemical and mechanical processes
enzymes speed up chemical reactions
1. Carbohydrases
  1. found in mouth, turns starch into glucose
    1. e.g. amylase
2. Proteases
  1. found in stomach, turns protein into amino acids
    1. e.g. pepsin
3. Lipases
  1. found in s. intestine, turns fats and oils into fatty acids and glycerol
    1. e.g. Lipase
Bile
1. strongly alkaline, neutralises stomach acid, ensures optimum conditions for enzymes in s.intestine to work
2. contains salts that break down fats and oils into small droplets
  1. Emulsification
    1. increases surface area of fats and oils to speed up their digestion
Absorption in the small intestine
1. inside wall is thin with large surface area
  1. absorption happens quickly and efficiently
  2. lined with villi
    1. increases surface area, more nutrients absorb faster
      1. increases rate of diffusion
    2. lacteals
      1. take away fat from s.i. to ensure there's a difference in concentration
        increases rate of diffusion
    3. blood capillaries
      1. take blood to different vessel, ensures there's a concentration gradient
        increases rate of diffusion
    4. One cell thick
      1. less distance for nutrients to travel
        absorption is quicker
Functional foods
1. have health-promoting benefits more than basic nutritional value
  1. probiotics
    1. contain bacteria to maintain healthy digestive system
      1. Bifidobacteria
  2. prebiotics
    1. contain added sugars that "feed" bacteria in alimentary canal
      1. Oligosaccharides
  3. Plant stanol esters
    1. come from plant stanols
      1. found naturally in food such as wheat and maize
        clinically proven to reduce absorption of cholesterol

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	Created by Sophia Durham about 10 years ago