digestive system

• Digestive system


  What it does, how it works, and the different organs involved
• 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 own digestive enzymes

  4. Pancreas produces and secretes digestive enzymes into small intestine

  5. Gallbladder secretes bile to neutralize stomach acid and emulsify fats
• Small intestine lining


  • 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
  • Stomach processes food
  • Enters small intestine
  • Digested food absorbed into bloodstream
  • Leftover material enters large intestine
  • Water absorbed, feces stored in rectum