digestive system

• 1. food enters mouth
  2. travels down oesophagus
  3. enters stomach
  4. small intestine
  5. large intestine
  6. rectum
• STEP ONE - MOUTH

  • food broken down by chewing
  • saliva helps it become more liquid
  • saliva contains salivary amylase which begins the digestion of starch
• STEP THREE - STOMACH

  • stomach contracts walls to move and mix food around
  • produced pepsin to break down protien
  • produces hydrochloric acid to kill any bacteria
• STEP FOUR - SMALL INTESTINE

  • the place where foods nutrients are absorbed into the blood stream
  • produces enzymes to break down food
  • contrains pancreatic juices ( from pancreas ) and bile ( from gall bladder )
• PANCREAS

  • produces lots of digestive enzymes in the form of pancreatic juices
  • secretes pancreatic juices into small intestine
• GALL BLADDER

  • stores bile made by the liver
  • secretes bile into the small intestine
  • Bile is an alkaline and neutralises the acids from the stomach making the PH more ideal of the enzymes to function
  • Bile emulsifies fats into small droplets which increases its surface area and makes it easier for enzymes to break down
• SMALL INTESTINE - EXCHANGE SURFACE ( how is it adapted to its function)

  • Lots of villi to increase surface area - meaning digested food can be absorbed into the blood stream much quicker
  • villi only have one layer of surface cells meaning nutrients only have to diffuse a short distance
  • good blood supply - maintains the concentration gradient
• STEP FIVE - LARGE INTESTINE

  • lots of food we eat isn’t digestible so passes through the large intestine
  • absorbs all the of excess water leaving behind waste which is stored in the rectum until removed