Digestive System


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Digestive System

  1. 1. Science : Biology : Digestion Digestion refers to the breaking down of large food molecules into smaller food molecules in the body. So that small food molecules can diffuse through the walls and enter bloodstream. Starch and proteins are large food molecules that cannot pass through the walls.
  2. 2. Nutrients <ul><li>Body needs energy to do work. </li></ul><ul><li>Nutrients include </li></ul><ul><ul><li>Carbohydrates </li></ul></ul><ul><ul><ul><li>Provide energy (growth, warmth, movement) </li></ul></ul></ul><ul><ul><li>Proteins </li></ul></ul><ul><ul><ul><li>For growth of cells and tissues </li></ul></ul></ul><ul><ul><ul><li>Repair of damaged tissues. </li></ul></ul></ul><ul><ul><ul><li>Source of energy if carbohydrates and fats unavailable </li></ul></ul></ul>
  3. 3. Nutrients <ul><li>Nutrients include </li></ul><ul><ul><li>Fats </li></ul></ul><ul><ul><ul><li>Provide energy </li></ul></ul></ul><ul><ul><ul><li>Two times that of carbohydrates </li></ul></ul></ul><ul><li>Nutrients help </li></ul><ul><ul><li>in our growth, </li></ul></ul><ul><ul><li>by keeping us healthy, </li></ul></ul><ul><ul><li>by repairing our cells and tissues, </li></ul></ul><ul><ul><li>by giving us energy. </li></ul></ul>
  4. 4. Enzymes : their role <ul><li>Enzymes are used to digest food </li></ul><ul><ul><li>Carbohydrase / Amylase </li></ul></ul><ul><ul><ul><li>Carbohydrates to Simple sugars </li></ul></ul></ul><ul><ul><li>Protease </li></ul></ul><ul><ul><ul><li>Proteins to Amino acids </li></ul></ul></ul><ul><ul><li>Lipase </li></ul></ul><ul><ul><ul><li>Fats to Glycerol and Fatty acids </li></ul></ul></ul>
  5. 5. Alimentary canal, organs and functions <ul><li>Alimentary canal consists of the </li></ul><ul><ul><li>Mouth (20sec) </li></ul></ul><ul><ul><ul><li>Starch (carbohydrate) is digested to maltose by carbohydrase / amylase </li></ul></ul></ul><ul><ul><li>Oseophagus (10sec) </li></ul></ul><ul><ul><ul><li>Walls of the alimentary canal are made of muscles which squeezes food along the canal. </li></ul></ul></ul><ul><ul><li>Stomach (2-6hrs) </li></ul></ul><ul><ul><ul><li>Produces gastric juice which mixes food when stomach churns. </li></ul></ul></ul><ul><ul><ul><li>Protease in the juice breaks down complex proteins into simpler ones </li></ul></ul></ul>
  6. 6. Organs joined to the Alimentary canal <ul><li>Liver </li></ul><ul><ul><li>Makes bile </li></ul></ul><ul><ul><ul><li>Greenish liquid which emulsifies fats, breaking them into smaller droplets, easier for lipase to digest it. </li></ul></ul></ul><ul><li>Gall bladder </li></ul><ul><ul><li>Stores bile </li></ul></ul><ul><li>Pancreas </li></ul><ul><ul><li>Creates pancreatic juice </li></ul></ul><ul><ul><ul><li>Flows to small intestine and contain enzymes </li></ul></ul></ul>
  7. 7. Alimentary canal, organs and functions <ul><li>Small intestine (5hrs) </li></ul><ul><ul><li>Produces intestinal juice which contains enzymes </li></ul></ul><ul><ul><li>Completes the digestion process with the help of the organs joined to the alimentary canal. </li></ul></ul>
  8. 8. Alimentary canal, organs and functions <ul><li>Digestion ends at the small intestine: </li></ul><ul><ul><li>Small molecules of digested food passes through the small intestine wall, into the bloodstream surrounding it. </li></ul></ul>
  9. 9. Digested food enters blood <ul><li>Digested food </li></ul><ul><ul><li>Made of small food molecules </li></ul></ul><ul><ul><ul><li>Diffuse through walls of small intestine </li></ul></ul></ul><ul><ul><ul><li>Into blood vessels in walls </li></ul></ul></ul><ul><ul><ul><li>Carried away by blood the rest of the body </li></ul></ul></ul><ul><ul><ul><li>Called absorption of food </li></ul></ul></ul><ul><ul><li>Blood carries the small food molecules to the cells of the body where they can be used. </li></ul></ul>
  10. 10. Easier absorption <ul><li>Finger-like villi </li></ul><ul><ul><li>Provides large surface area </li></ul></ul><ul><ul><li>Folds the cell membrane </li></ul></ul><ul><li>7 m-long small intestine </li></ul><ul><ul><li>Increases surface area </li></ul></ul><ul><li>One-cell thick small intestine </li></ul><ul><ul><li>Shortens distance between wall and bloodstream </li></ul></ul>
  11. 11. Alimentary canal, organs and functions <ul><li>Alimentary canal consists of the </li></ul><ul><ul><li>Large intestine and anus (24hrs) </li></ul></ul><ul><ul><ul><li>Undigested food reaches the large intestine </li></ul></ul></ul><ul><ul><ul><li>Lots of water is removed and taken back into the body </li></ul></ul></ul><ul><ul><ul><li>Pass out through anus as faeces </li></ul></ul></ul>
  12. 12. Summary : Digestion of foods <ul><li>Nutrients in foods </li></ul><ul><ul><li>Carbohydrates and fats are used for respiration and as sources of energy. </li></ul></ul><ul><ul><li>Proteins are used for growth and the repair of body tissues. </li></ul></ul><ul><ul><li>Starch and glucose are two kinds of carbohydrates. </li></ul></ul><ul><li>Why digestion is needed </li></ul><ul><ul><li>Only small molecules are able to pass through cell membranes into cells. </li></ul></ul><ul><ul><li>Starch, fat and protein molecules are too large to pass through. </li></ul></ul>
  13. 13. Summary : Digestion of foods <ul><li>Meaning of digestion </li></ul><ul><ul><li>Digestion is the breaking down of large food molecules in the body into small food molecules. </li></ul></ul><ul><ul><li>The small food molecules are: glucose (from starch), amino acids (from proteins) and glycerol and fatty acids (from fats). </li></ul></ul><ul><ul><li>Digestion takes place by the action of enzymes. </li></ul></ul>
  14. 14. Summary : Digestion of foods <ul><li>The alimentary canal and digestion </li></ul><ul><ul><li>Mouth </li></ul></ul><ul><ul><ul><li>Digestion of starch begins here. </li></ul></ul></ul><ul><ul><li>Stomach </li></ul></ul><ul><ul><ul><li>Digestion of proteins begins here. </li></ul></ul></ul><ul><ul><li>Small intestine </li></ul></ul><ul><ul><ul><li>Most digestion takes place here. </li></ul></ul></ul><ul><ul><ul><li>Digestion of starch and proteins is completed here. </li></ul></ul></ul><ul><ul><ul><li>Digestion of fats takes place only in the small intestine. Absorption of digested food </li></ul></ul></ul><ul><ul><ul><li>The small, digested food molecules are absorbed into the bloodstream through the walls of the small intestine. </li></ul></ul></ul><ul><ul><ul><li>The villi of the small intestine increase the surface area for faster absorption of small, digested food molecules . </li></ul></ul></ul>