The digestive system

• Food contain three main nutrients: carbohydrates (eg starch), protein and lipids (fats). All these molecules too big to be absorbed into blood stream, therefore have to be digested
• During digestion, large food molecules are broken down into small molecules by enzymes. The small molecules can then be absorbed into the blood stream
• Mouth contains salivary glands which produce saliva containing amylase that breaks down starches into sugars

  
• Food is chewed, enzymes in saliva begin to digest the starch into smaller sugar molecules

  
• food passes down the oesophagus into the stomach, enzymes begin digestion of proteins. Stomach also contain hydrochloric acid which help the enzymes digest proteins

  
• The stirring action of the stomach muscles turns the food into a fluid increasing the surface area for enzymes to digest

  
• The fluid passes into the small intestine

  
• At this point chemicals are released into the small intestine from the liver and pancreas

  
• The pancreas releases enzymes which continue the digestion of starch and protein. They also start the digestion of lipids
• The liver releases bile which helps speed up the digestion of lipids. Bile also neutralises the acid released from the stomach
• The wall of the small intenstine release enzymes to continue the digestion of protein and lipids
• In the small intestine, the small food molecules produced by digestion are absorbed into the bloodstream either by diffusion or by active transport
• from small intestine to large intestine where water is absorbed into the bloodstream and then poop is released from body
• 1 - In the digestive system large food molecules are digested into smaller molecules and then the products of digestion are absorbed into the blood stream
• 2 - now the products of digestion are then used by the body to build new carbohydrates, lipids and proteins
• 3 - some of the glucose produced is used in respiration
• Tissue

  A group of cells with a similar structure and function
• Organ

  A group of tissues working together for a specific function
• Organ system


  Organs grouped together to form organisms
• Main nutrients in food

  • Carbohydrates
  • Protein
  • Lipids (fats)
• Digestion

  1. Large food molecules broken down into small molecules by enzymes

  2. Small molecules absorbed into bloodstream
• Main organs of the digestive system

  • Mouth
  • Esophagus
  • Stomach
  • Small intestine
  • Large intestine
  • Liver
  • Pancreas
• Mouth

  • Food chewed, enzymes in saliva begin to digest starch
• Esophagus

  • Food passes from mouth to stomach
• Stomach

  • Enzymes begin digestion of proteins, contains hydrochloric acid, churning action turns food into fluid
• Small intestine

  • Chemicals from liver and pancreas continue digestion of starch, protein and lipids
  • Small food molecules absorbed into bloodstream
• Large intestine

  • Water absorbed, feces released
• Liver

  • Releases bile to aid digestion of lipids, neutralizes stomach acid
• Pancreas

  • Releases enzymes to continue digestion of starch, protein and lipids
• Products of digestion used by body to build new carbohydrates, lipids and proteins
• Some glucose produced is used in respiration