Digestion + absorption

• Digestion


  The breaking down of large, insoluble food molecules into small, soluble molecules that can be absorbed
• Absorption


  The process in which small, soluble food molecules are transferred from the gut to the blood system (in the ileum)
• Main groups of enzymes in the digestive system


  • Carbohydrase (amylase)
  • Protease
  • Lipase
• Carbohydrase (amylase)


  Digests starch
• Protease


  Digests protein
• Lipase


  Digests fat
• Ileum


  • Very large surface area due to its length, presence of folds (or twists) and villi
  • Good blood supply
  • Thin and permeable membranes
• Villi are microscopic 'finger-like' extensions on the inner surface of the ileum
• Absorption in the ileum

  1. Lacteal absorbs breakdown products of fat (glycerol and fatty acids) and returns them to the blood later

  2. Capillary network in the villus absorbs breakdown products of protein (amino acids) and starch (glucose)
• Alimentary canal


  Another name for the digestive system
• Functions of the digestive process


  • Ingestion: taking food into the body
  • Digestion: break down of insoluble substances into soluble ones
  • Absorption: Uptake of soluble substances into cells
  • Assimilation: how cells use food
  • Egestion: removal of undigested waste
• Food is broken down into smaller pieces by biting, chewing, churning, bile action
• Enzymes break chemical bonds to make insoluble food particles soluble
• What enzymes break down


  • Carbohydrases break down carbohydrates
  • Proteases break down proteins
  • Lipases break down lipids
• Ileum


  • Very long (5m)
  • Has many folds and villi
  • Large surface area for absorption
  • Good blood supply
  • Thin and permeable membranes
• The absorbed nutrients, amino acids and sugars are carried in the blood to the liver in the hepatic portal vein
• Organ systems in the human body

  • Digestive
  • Respiratory
  • Nervous
  • Circulatory
  • Excretory
  • Reproductive
  • Skeletal