Organization

• Humans have to eat loads of food which is mostly used for energy so that we can move about and keep our metabolism running
• Main groups of nutrients needed


  • Carbohydrates (like starch and glucose)
  • Proteins
  • Fats
• Role of digestion


  To break all this food down into tiny pieces so that we can absorb it into our body cells
• Digestion process


  1. Physical breakdown (chewing)

  2. Chemical breakdown by enzymes
• Mouth


  1. Food placed in mouth

  2. Broken down physically by chewing

  3. Saliva released from salivary glands

  4. Saliva contains salivary amylase to break down carbohydrates
• Esophagus


  Food swallowed and passes down
• Stomach


  1. Muscular sac that contracts to push and mix food

  2. Produces pepsin enzyme to break down proteins

  3. Produces hydrochloric acid to kill bacteria and provide right environment for pepsin
• Small intestine


  1. Digested food absorbed into bloodstream

  2. Site of most digestion

  3. Produces digestive enzymes

  4. Pancreas produces and releases digestive enzymes

  5. Gallbladder releases bile to neutralize acid and emulsify fats
• Lining of small intestine

  • Villi (finger-like projections) to increase surface area
  • Single layer of surface cells for short diffusion distance
  • Good blood supply to maintain concentration gradient
• Large intestine


  1. Absorbs excess water from leftover material

  2. Stores feces in rectum until removal
• Recap of digestive process order

  • Food placed in mouth
  • Chewed and mixed with saliva
  • Swallowed down esophagus
  • Enters stomach
  • Pushed into small intestine
  • Digested and absorbed into bloodstream
  • Leftover material enters large intestine
  • Water absorbed, feces stored in rectum
• Enzymes

  Essential for helping us break down the large molecules that we eat into the much smaller soluble molecules that we can absorb through our intestinal lining
• Main groups of nutrients to be broken down

  • Carbohydrates
  • Proteins
  • Fats
• Carbohydrates


  Found mainly in foods like pasta, potatoes and rice, used by the body mainly as an energy source
• Starch


  The main type of carbohydrate
• Breakdown of starch


  Broken down by the enzyme amylase into smaller sugars such as maltose
• Places where amylase is made

  • Salivary glands
  • Pancreas
  • Small intestine
• Proteins


  Found in things like nuts, meats and beans
• Breakdown of proteins


  Broken down by protease enzymes into amino acids
• Places where proteases are made

  • Stomach (pepsin)
  • Pancreas
  • Small intestine
• Fats/Lipids


  Found in foods like cheese, oils and chocolate
• Breakdown of fats/lipids


  Broken down by lipase enzymes into glycerol and fatty acids
• Places where lipases are made

  • Pancreas
  • Small intestine
• All digestive enzymes are made by the pancreas and small intestine, with amylase also made by salivary glands and proteases also made in the stomach