Biology: Organisation

• Overview of the main functions of the different organs in the digestive system

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

  2. Food passes down the esophagus into the stomach where enzymes begin the digestion of proteins

  3. Stomach contains hydrochloric acid which helps digest proteins

  4. Churning action of stomach muscles turns food into a fluid increasing surface area for enzyme digestion

  5. Fluid passes into the small intestine where chemicals are released from the liver and pancreas

  6. Pancreas releases enzymes to continue digestion of starch, protein, and lipids

  7. Liver releases bile to speed up digestion of lipids and neutralize stomach acid

  8. Fluid moves through the rest of the small intestine where walls release enzymes to continue digestion

  9. Small food molecules produced by digestion are absorbed into the bloodstream in the small intestine

  10. Fluid moves through the large intestine where water is absorbed into the bloodstream

  11. Feces is finally released from the body
• Cells are often specialized with adaptations to help them carry out their function
• Muscle cells


  Can contract, contain special protein fibers for changing length, have plenty of mitochondria for energy needed for contraction
• Tissue


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


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


  Group of organs working together to form organisms
• Main nutrients found in food

  • Carbohydrates (starch), Protein, Lipids (fats)
• Large food molecules


  • Carbohydrates, Protein, Lipids
• Large food molecules are too large to be absorbed into the bloodstream, so they have to be digested into small molecules by enzymes
• Small molecules produced by digestion are absorbed into the bloodstream
• Products of digestion are used by the body to build new carbohydrates, lipids, and proteins
• Glucose produced is used in respiration