digestive system

• Digestive system


  The body needs food for energy. The food we eat is composed of nutrients. The role of the digestive system is to break down these nutrients and pass them into the bloodstream
• Digestive system


  • It is made up of a 9 meter tube (that's broken into sections) which the food passes through
  • Associated organs – the salivary glands, pancreas and liver which aid in the digestion process
• Nutrition involves 5 stages

  1. Ingestion: Taking food into the mouth

  2. Digestion: Breaking down the food into simpler molecules

  3. Absorption: Simple food molecules pass through the intestines into the blood

  4. Assimilation: The nutrients are put to use by the body

  5. Egestion: Waste is excreted
• Physical digestion


  Breaking down the food into smaller pieces using the teeth
• Types of teeth


  • Incisors
  • Canines
  • Premolars
  • Molars
• Chemical digestion


  The salivary glands produce saliva which helps break down food chemically
• Peristalsis


  A wave of muscular contractions that pushes food down the digestive system
• Stomach


  • It is a muscular bag lined with a thick layer of mucus to prevent acid and digestive enzymes from damaging the wall
  • Physical digestion: Food is churned around the stomach
  • Chemical digestion: food is mixed with Hydrochloric Acid and Enzymes to help break down the food further
• Small intestine


  • It is 6 meters long giving it a large surface area to absorb nutrients
  • It has millions of tiny finger like projections called VILLI
  • The villi are one cell thick and have a huge blood supply which allows nutrients to be absorbed back into the blood stream
• Large intestine


  Reabsorption of water from the remaining undigested food
• Waste (Egestion)


  The remaining material is stored as waste in the rectum until it is egested as faeces through the anus
• Liver


  • It produces bile which helps break up fat
  • It is stored in the GALL BLADDER
  • It also helps break down toxic materials such as alcohol
• Pancreas


  • Releases pancreatic juice which helps with digestion
  • Releases insulin which helps maintain blood sugar levels
• Enzymes


  • Biological catalyst (speed up reaction)
  • Substrate
  • Product
• Enzyme


  • Amylase
  • Starch
  • Maltose