small intestine

• three regions of the small intestine

  duodenum, jejunum, ileum
• what is the duodenum

  the first 30 cm of the small intestine in the shape of a 'C'
• what does the duodenum do

  it completes the digestion of protein and starts the hydrolysis of carbohydrates and lipids
• how is the duodenum adapted for digestion

  • glands in the gut wall secrete intestinal juice containing all the enzymes needed (carbohydrate, protease, and lipase) to complete chemical digestion.
  • digestive enzymes are also released from pancreatic juice
  • bile is made by the liver and stored in the gallbladder is used to create an alkaline environment. bile also helps to emulsify fats, its an antiseptic and it promotes peristalsis. pancreatic juice and intestinal juice also contain alkaline salts to do this
• what does secretin do

  when acidic chyme enters the duodenum id stimulates this hormone which in return stimulates the production of intestinal juice
• what pH does intestinal and pancreatic juices have and why

  a slightly alkaline pH to create and alkaline environment for the enzymes as well as neutralizing the acidic chyme
• What happens in the ileum


  Final of digestion but it’s main role is absorption
• how is the ileum adapted for digestion

  • peristakiss psuhes chyme slowly allowing for more absorption
  • it is very long so it allows for a larger surface area
  • it is lined with millions of villi
• How big is a villi

  1mm long
• How is the villi adapted for absorption

  • it has blood capillaries and a central lymph vessel (lacteal) to transport absorbed substances
  • It is covered with a single layer of columnar epithelium for faster diffusion and absorption
  • the epithelium cells have microvilli to further increa their surface area
  • special epithelium cells called goblet cells to release mucus to protect the gut lining
  • muscles in the villus cause it to move and increase contact with nutrients