Guide

• Organs of the digestive system

  • Tongue
  • Salivary glands
  • Epiglottis
  • Liver
  • Gall bladder
  • Duodenum
  • Caecum
  • Appendix
  • Oesophagus
  • Stomach
  • Pancreas
  • Ileum
  • Colon
  • Rectum
  • Anus
• Tongue

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• Salivary glands


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• Epiglottis

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• Liver


  • Secretes bile via the gall bladder and bile duct
• Gall bladder


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• Duodenum

  • 
    
• Caecum

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• Appendix

  • 
    
• Oesophagus

  • 
    
• Stomach

  • 
    
• Pancreas

  • 
    
• Ileum

  • 
    
• Colon

  • 
    
• Rectum

  • 
    
• Anus

  • 
    
• You need to be able to recall the location of the organs of the digestive system
• Epithelium


  Innermost layer of the gut wall, site of absorption and secretion of mucus
• Mucosa


  Innermost layer of the gut wall, lined with epithelium
• Submucosa


  Contains connective tissue, nerves, blood and lymph capillaries
• Muscle layers


  Help move food by peristalsis
• Serosa


  Outer layer made of thick connective tissue
• You must know the histology of the gut and the layers of the gut wall
• All enzyme reactions are hydrolysis reactions
• Endopeptidases


  Break protein from long chains into short chains
• Exopeptidases


  Finish protein digestion by hydrolysing short chain polypeptides into amino acids
• Endopeptidases are always secreted in their inactive form and then get activated outside the cell to stop the enzyme from digesting cell proteins
• Pepsin


  Secreted as inactive pepsinogen by gastric glands and converted into pepsin by hydrochloric acid
• Trypsin


  Secreted as inactive trypsinogen by the pancreas and converted into trypsin by the enzyme enterokinase
• Saliva


  Lubricates food
• Chewing


  Mechanical digestion
• Peristalsis


  Movement of food
• Churning


  Mechanical digestion
• Partial intestine


  What is digested?
• Mouth


  Starch and glycogen digested by Amylase from Salivary glands
• Stomach


  Protein digested by Pepsin (from Pepsinogen activated by acid), Lipids digested by Lipase
• Stomach


  Acidic pH optimum
• Duodenum


  Lipids digested by Pancreatic Lipase, Protein digested by Trypsin, Starch digested by Pancreatic Amylase, Polypeptides digested by Peptidase
• Duodenum


  Sucrose digested by Sucrase, Lactose digested by Lactase
• Colon


  Absorption of water and soluble vitamins, Alpha-glucose digested