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
• Swallowing


  Food passes down the gullet/esophagus
• 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. Where digested food is absorbed into bloodstream

  2. Produces digestive enzymes to aid digestion

  3. Pancreas produces and pushes digestive enzymes into small intestine

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

  • Has finger-like projections called villi to increase surface area
  • Only has a single layer of surface cells so nutrients only have to diffuse a short distance
  • Has a 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 full digestive process

  1. Food placed in mouth, chewed and mixed with saliva

  2. Swallowed down esophagus into stomach

  3. Stomach mixes and breaks down food

  4. Food passes into small intestine, mixed with pancreatic juices and bile

  5. Digested food absorbed into bloodstream

  6. Leftover material passes into large intestine, water absorbed, feces stored in rectum