Parts of the digestive system

The digestive system and what each part does

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Buccal cavity

  • Teeth. Canines rip/tear, incisors bite and molars chew.
  • Salivary amylase: hydrolyses starch to maltose.
  • Buffers: neutralise acid.
  • Mucoproteins: lubricate
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Epiglottis

  • Protects the larynx during swallowing
  • CLoses over the trachea to prevent choking
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Oesophagus

  • Circular muscles squeeze food down to the cardiac sphincter using peristalsis.
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Stomach

  • Highly elasticated muscular organ
  • Wall:highly folded and dotted with gastric pits.
  • Food churned into CHYME
  • Mucus comes from goblet cells
  • HCl comes from oxyntic cells
  • Pepsinogen comes from chief cells. It hydrolyses polypeptides into smaller polypeptides.
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Duodenum

  • First part of small intestine.
  • Pyloric sphincter controls exit of the stomach.
  • Almost all digestion occurs here.
  • No villi
  • Where pancreatic juices are used.
  • Exopeptidases: hydrolyse peptide bonds at end of polypeptides.
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Pancreas

  • Large gland situated below the stomach.
  • Produces pancreatic juice.
  • pancreatic amylase: digests starch into maltose
  • pancreatic endopeptidases: digest proteins into short peptides
  • Pancreatic lipase: digest triglycerides to fatty acids and glycerol
  • Pancreatic nucleases: hydrolyse DNA and RNA to nucleotides
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Liver

  • Secretes bile, which aids with digestion
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Gall bladder

  • Stores bile and BILE SALTS
  • Helps lipid digestion by emulsifying them
  • Neutralises stomach acid
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Jejunum

  • 2m long
  • Large folding of mucosa, then villi, then microvilli
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Ileum

  • 4m long
  • Final site of digestion and absorption
  • Numerous glands in the mucosa and submucosa secrete enzymes, mucus and NaHCO3
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Appendix

  • Not needed any more
  • Originally to break down the cellulose found in grass etc
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Caecum

  • Water is absorbed from semi solid faeces.
  • Mucosa has villi, but no microvilli.
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Colon

  • Faeces contain cellulose, cholesterol, bile, mucus, cells, bacteria and water
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Rectum and ****

  • Rectum is the final section of the intestine where the faeces are stored.
  • Anus is where egestion occurs. This is controlled by the anal sphincter
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