Major Parts of the Digestive System

The structure and function of the main parts of the digestive system

The Oesophagus

  • carries food from the mouth to the stomach
  • therefore it's adapted for transport rather than for digestion or absorption
  • made up of a thick muscular wall
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The Stomach

  • muscular sac
  • inner layer produces enzymes
  • role = store and digest foods (especially protiens)
  • has glands - produce enzymes which digest protien
  • other glands in stomach wall produce mucus
  • mucus prevents stomach being digested by it's own enzymes
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The Small Intestine

  • long muscular tube
  • food is further digested by enzymes
  • enzymes - produced in walls and by glands that pour their secretions into it
  • inner walls folded into villi - gives large surface area
  • millions of tiny projections called microvilli, on the epithelial cells of each villus - increases surface area
  • this adapts the small intestine for its purpose - absorbing products of digestion into the bloodstream
  • larger surface area=increased rate of absorption
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The Large Intestine

  • absorbs water
  • most of the water thats reabsorbed comes from the secretions of the many digestive glands
  • therefore the food within the large intestine becomes drier and thicker - forms faeces
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The Rectum

  • final section of the intestines
  • faeces are periodically stored here
  • before being removed via the anus - during egestion
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The Salivary Glands

  • situated near the mouth
  • pass their secretions via a duct into the mouth
  • secretions contain amylase - breaks down starch into maltose
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The Pancreas

  • large gland
  • situated below the stomach
  • produces and secretes pancreatic juice
  • this contains protease, lipase and amylase
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