small intestine

• Small intestine

  Long muscular tube that contracts and relaxes to mix food with digestive enzymes for further digestion
• Small intestine

  • Has numerous tiny blood vessels in its walls, close to the lining, to bring oxygen needed by the cells and take away the carbon dioxide they produce
  • Absorbs the digested food from the alimentary canal
• Digestion in the small intestine

  1. Small intestine, pancreas and liver produce intestinal juice, pancreatic juice and bile

  2. Bile, pancreatic juice and intestinal juices are passed into the small intestine to help digestion
• Bile


  Fluid produced by the liver that helps to break up lipids into smaller lipid droplets - emulsification
• Emulsification

  Increases surface area of lipids to allow the lipases in pancreatic juice and intestinal juices to digest lipids quickly
• Intestinal juice


  Contains the enzymes such as maltase, protease and lipase
• Pancreatic juice


  Contains the enzymes such as amylase, protease and lipase
• Digestion of lipid

  Catalysed by lipase to fatty acids and glycerol
• Digestion of starch

  1. Catalysed by amylase in pancreatic juice to maltose

  2. Then by maltase in intestinal juice to glucose
• Digestion of a simpler protein molecule

  Catalysed by protease to amino acids
• Absorption in the small intestine

  Only small food molecules pass through the wall of the small intestine into the blood vessels
• Absorption of food molecules

  1. Transported in the bloodstream

  2. Absorbed by body cells through their plasma membranes
• Use of food molecules

  For respiration, cell repair and other processes
• Digestion ends

  1. Remaining undigested food contains mostly fibre

  2. Together with some water and mineral salts, undigested food passes into the large intestine