The human digestive system

• The human digestive system has two functions:

  • breaks down complex food substances
  • provides a very large surface area for maximum absorption of food
• The structure of the digestive system

  Regions of the digestive system are adapted to the digestion and absorption of food:

  
• Mouth: Begins the digestion of carbohydrates
• Stomach: Begins the digestion of protein; small molecules such as alcohol absorbed
• Small intestine - Duodenum: Continues the digestion of carbohydrates and protein; begins the digestion of lipids
• Small intestine - Ileum: Completes the digestion of carbohydrates and proteins into single sugars and amino acids; absorption of single sugars, amino acids and fatty acids and glycerol
• Large intestine: Absorption of water; egestion of undigested food
• Digestive enzymes are used to break down food in the gut into small, soluble molecules that can be absorbed through the gut wall.