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  1. 2. Why Do We Need to Digest? <ul><li>Nutrients from food provides us with the energy and materials we need for work, growth and repair </li></ul><ul><li>The problem is that most of the nutrients we need cannot be used in the form they are eaten </li></ul><ul><li>Nutrients need to be broken up into their smallest components in order to diffuse into our blood stream </li></ul>
  2. 3. What needs to be broken up? <ul><li>Carbohydrates  simple sugars </li></ul><ul><li>Proteins  amino acids </li></ul><ul><li>Fats  Glycerol and fatty acids </li></ul><ul><li>Enzymes </li></ul><ul><li>Type of protein that breaks food molecules into smaller units. </li></ul>
  3. 4. The Process of Digestion <ul><li>Divided into 3 stages: </li></ul><ul><li>Physical Digestion </li></ul><ul><ul><li>Taking food in – Cutting and chewing food </li></ul></ul><ul><li>Chemical Digestion </li></ul><ul><ul><li>Enzymes break down food even further </li></ul></ul><ul><li>Absorption </li></ul><ul><ul><li>Wastes are excreted </li></ul></ul>
  4. 6. Mouth <ul><li>Physical digestion starts starch digestion </li></ul>Esophagus Rapid passage of food to stomach
  5. 7. Stomach <ul><li>Digestion of proteins </li></ul>Liver <ul><li>Digestion of proteins </li></ul>
  6. 8. Pancreas <ul><li>Production of many enzymes which digest all types of food </li></ul>Small Intestine Production of more enzymes and absorption of most end products
  7. 9. Large Intestine <ul><li>Reabsorption of water </li></ul>Rectum Temporary storage of undigested waste
  8. 10. Elimination <ul><li>Removal of undigested wastes </li></ul>
  9. 11. <ul><li>On your plate with a fork and knife </li></ul><ul><li>Your saliva initiates chemical digestion with an enzyme that breaks carbohydrates down into simple sugars </li></ul><ul><li>Your teeth and tongue break up food into smaller pieces and grind it up </li></ul>
  10. 12. Stage 1
  11. 13. Physical Digestion - Teeth <ul><li>Adult humans have 4 different kinds of teeth (32 total) </li></ul><ul><li>Incisors at the very front (4 on top, 4 on bottom) </li></ul><ul><li>Canines (cuspids) beside the incisors and are pointed (4 total) </li></ul><ul><ul><ul><ul><li>Used for tearing or shredding </li></ul></ul></ul></ul><ul><li>Premolars (8 total) </li></ul><ul><li>Molars (12 total incl. wisdom teeth) </li></ul><ul><li>Premolars + molars – flattened on upper surface, used for grinding and chewing tough food </li></ul>
  12. 14. <ul><li>Children have deciduous or primary teeth (20 total) </li></ul><ul><li>8 Incisors </li></ul><ul><li>4 Canines </li></ul><ul><li>8 molars </li></ul>
  13. 15. Parts of the Teeth <ul><li>Crown - visible part above the gum </li></ul><ul><li>Root – Part below the gum line, holds tooth in place </li></ul><ul><li>Enamel – protective coating – hardest substance in the body, cannot be replaced. </li></ul>
  14. 16. Parts of the Teeth <ul><li>Dentine – hard bone that gives teeth shape and strength. It is sensitive to temperature, sugar, touch, acids, etc. </li></ul><ul><li>Pulp Chamber – message center for sensation in the dentine </li></ul><ul><li>Gum line – help hold and protect teeth </li></ul>
  15. 17. Parts of the Teeth <ul><li>Root Canal – carries blood and nerve endings </li></ul><ul><li>Cementum – connect tooth to the jaw bone </li></ul>
  16. 19. <ul><li>Carnivores – Sharp teeth for grabbing food and ripping it apart </li></ul><ul><li>Herbivores – Flat teeth for grinding food </li></ul><ul><li>Omnivores – Flat and sharp teeth </li></ul>
  17. 20. What causes tooth decay? <ul><li>Bacteria called plaque live in your mouth </li></ul><ul><li>Plaque eats any food that stays on your teeth </li></ul><ul><li>Produce acid that eats away the enamel, creating pits called cavities </li></ul><ul><li>Build up of a hard crust called tartar </li></ul><ul><li>NOTE: Sugar does not cause tooth decay, it feeds the bacteria that do </li></ul>
  18. 21. Brushing and flossing removes plaque and keeps gums healthy Wear mouth guards in sports Regular dental checkups (clean away tartar) Diet: calcium, phosphorus, vitamins A, C & D all help maintain teeth and gums
  19. 22. Some Dental Problems <ul><li>Sensitivity due to the removal of enamel by cavities and exposing dentine </li></ul><ul><li>Abscesses – bacteria get into the root and infect it </li></ul><ul><li>Peridontal Disease – Affect the tissue around the teeth. Includes retreating gum line, sore gums or bleeding. Usually caused by poor diet or hygiene. </li></ul><ul><li>Halitosis – bad breath caused by smoking, infections, tooth decay, sinus infections, etc. </li></ul>
  20. 24. Stage 2
  21. 25. Begins In the Mouth <ul><li>Amylase </li></ul><ul><li>1 st enzyme to act. </li></ul><ul><li>Produced by saliva </li></ul><ul><li>Helps break down starch into sugar molecules. </li></ul>
  22. 26. Saliva <ul><li>Produced by 3 pairs of glands inside the mouth </li></ul><ul><li>Is slightly acidic </li></ul><ul><li>Approx 1000 mL produced per day ! </li></ul><ul><li>99% is water </li></ul>
  23. 27. Function of Saliva <ul><li>Moistens dry food </li></ul><ul><li>Binds the loose crumbs together so bits do not get into the respiratory system </li></ul><ul><li>Softens food so rough edges will not scratch the walls </li></ul><ul><li>Enzyme amylase begins chemical digestion </li></ul>
  24. 28. <ul><li>Hard Palate </li></ul><ul><li>Soft Palate </li></ul><ul><li>Uvula </li></ul>
  25. 29. The Tongue <ul><li>Attached to the floor of the mouth </li></ul><ul><li>Helps to move food to the molars </li></ul><ul><li>Mixes food with saliva </li></ul>
  26. 30. The Tongue <ul><li>Once the food is moist and soft, the tongue rolls it into a ball called a bolus . </li></ul><ul><li>This prepares the food to pass into the pharynx to be swallowed. </li></ul>
  27. 32. Swallowing <ul><li>The tongue moves the bolus of swallowed food to the back of the mouth </li></ul><ul><li>The soft palate moves upward to partially seal off the nasal passage </li></ul><ul><li>At the same time, the epiglottis closes the opening into the respiratory passage </li></ul>
  28. 34. <ul><li>Place cracker in mouth </li></ul><ul><li>Chew WITHOUT SWALLOWING! </li></ul><ul><li>Note the taste </li></ul><ul><li>Leave on tongue until you notice a taste change (can take up to 5 min) </li></ul><ul><li>What do you taste? </li></ul>
  29. 35. The Sense of Taste <ul><li>Humans detect taste with taste receptor cells </li></ul><ul><li>These are clustered into taste buds </li></ul><ul><li>Taste buds are clustered into bumps called papillae </li></ul><ul><li>There are 5 primary taste sensations </li></ul><ul><ul><li>salty </li></ul></ul><ul><ul><li>sour </li></ul></ul><ul><ul><li>sweet </li></ul></ul><ul><ul><li>bitter </li></ul></ul><ul><ul><li>Umami (Savory) </li></ul></ul>
  30. 37. <ul><li>The movement of food from the tongue down into the pharynx is under voluntary control </li></ul><ul><li>The second stage, involving the epiglottis and the movement of the food into the esophagus, is involuntary </li></ul>
  31. 38. The Esophagus <ul><li>Flexible tube – approx. 25 cm long </li></ul><ul><li>Leads from the pharynx to the stomach </li></ul><ul><li>Walls have 2 layers of muscle </li></ul><ul><li>The inner lining covered with mucus – helps food pass through easily </li></ul>
  32. 39. Peristalsis <ul><li>Bolus is moved through peristaltic action </li></ul><ul><li>Peristalsis - the rhythmic contractions of muscles – like squeezing a tube of tooth paste </li></ul>
  33. 40. <ul><li>Cardiac sphincter: </li></ul><ul><ul><li>Ring of muscle that controls the passage of bolus into stomach </li></ul></ul><ul><ul><li>– like pulling a drawstring </li></ul></ul>
  34. 41. The Stomach <ul><li>Large muscular bag that stretches as it fills with food </li></ul><ul><li>Can hold 1.5 L </li></ul><ul><li>Made up of many layers, including 3 layers of muscle </li></ul>
  35. 42. <ul><li>Gastric glands produce gastric juice . </li></ul><ul><ul><li>Pepsin (an enzyme) – Breaks down protein </li></ul></ul><ul><ul><li>Hydrochloric Acid </li></ul></ul><ul><li>The muscular walls of the stomach contract to mix food with gastric juice, producing a mixture called chyme . </li></ul>
  36. 43. Hydrochloric Acid (HCL) <ul><ul><li>Lowers the pH of the stomach to allow enzymes to work efficiently </li></ul></ul><ul><ul><li>Helps kill bacteria </li></ul></ul><ul><ul><li>Mucus secretions protect the stomach walls from HCl </li></ul></ul><ul><ul><li>BUT sometime mucus is not enough and HCL and digestive enzymes eat away at the lining, resulting in a peptic ulcer . </li></ul></ul>
  37. 44. Heart Burn <ul><li>Presence of stomach acid in the esophagus </li></ul><ul><li>Cardiac sphincter is not working properly – opens allowing acidic stomach contents into the esophagus </li></ul>
  38. 45. <ul><li>http://videos.howstuffworks.com/hsw/17648-food-into-fuel-the-process-of-digestion-video.htm </li></ul>
  39. 46. <ul><li>The pyloric sphincter is located at the lower end of the stomach </li></ul><ul><ul><li>Controls the flow of partially digested food (Chyme) out of the stomach </li></ul></ul>
  40. 47. The Small Intestine <ul><li>2.5 cm in diameter, and is about 7m in length </li></ul>Esophagus Stomach Small Intestine
  41. 48. Small Intestine <ul><li>A long coiled and looped tube </li></ul><ul><li>Fills most of the abdomen </li></ul><ul><li>Held in place by a membrane called mesentery </li></ul>
  42. 49. 4 functions of the Small Intestine <ul><li>Keeps the food moving by peristalsis </li></ul><ul><li>Secretes enzymes which continue the digestive process </li></ul><ul><li>The site where digestion by chemicals from the pancreas and liver take place </li></ul><ul><li>Nutrients are absorbed into the bloodstream </li></ul>
  43. 50. Digestive processes… <ul><li>3 basic food substances in the small intestine: </li></ul><ul><ul><li>Carbohydrates </li></ul></ul><ul><ul><li>Fats </li></ul></ul><ul><ul><li>Proteins </li></ul></ul><ul><li>They are broken down into molecules that are small enough to pass through the wall and enter the circulatory system </li></ul>
  44. 51. The Pancreas <ul><li>Produce pancreatic juice – which contain about 28 enzymes and sodium bicarbonate </li></ul><ul><ul><li>Lipase – breaks down fat </li></ul></ul><ul><ul><li>Amylase – completes carbohydrate digestion </li></ul></ul><ul><ul><li>Trypsin and peptidase – complete protein digestion </li></ul></ul><ul><li>Sodium bicarbonate neutralizes the acidic chyme as it comes out of the stomach </li></ul>
  45. 52. How are our bodies built to handle the acid in our stomach?
  46. 54. The Liver <ul><li>Produces bile that is stored in the gall bladder </li></ul><ul><li>Bile emulsifies fat – which means that it helps fat dissolve in water so it can be digested and absorbed </li></ul>
  47. 56. Absorption Stage 3
  48. 57. Absorption of Nutrients <ul><li>Villi: </li></ul><ul><li>Increase surface area for absorption </li></ul><ul><li>Collect the nutrients and transport them to where they are needed in the body </li></ul><ul><ul><li>Surface of the small intestine is folded </li></ul></ul><ul><ul><li>Covering the surface are projections called villi </li></ul></ul>
  49. 58. <ul><li>Reabsorption and Elimination: The Large Intestine </li></ul>
  50. 59. The Large Intestine consists of: <ul><li>Cecum </li></ul><ul><li>Appendix </li></ul><ul><li>Colon </li></ul><ul><li>Rectum </li></ul>
  51. 60. The Large Intestine <ul><li>Approx. 1.5 m in length </li></ul><ul><li>7.6 cm in diameter </li></ul><ul><li>Functions mainly to reabsorb water </li></ul>
  52. 61. <ul><li>Appendix </li></ul><ul><ul><li>Believed to have no function </li></ul></ul><ul><ul><li>Can become infected –called appendicitis </li></ul></ul>Cecum – Where the small intestine empties into the large intestine
  53. 62. Large Intestine function <ul><li>Reabsorbs water and maintains the fluid balance of the body </li></ul><ul><li>Absorbs certain vitamins </li></ul><ul><li>Undigested food is dried into suitable consistency for defecation </li></ul><ul><li>Stores waste before it is eliminated </li></ul>
  54. 63. The Rectum <ul><li>Last section of the digestive tract </li></ul><ul><li>Ends with the anal sphincter (like a drawstring) </li></ul><ul><li>When full there is a mild feeling of discomfort, which tells us that the feces is ready to be eliminated </li></ul>
  55. 64. What Your Feces Can tell you… <ul><li>Feces are 75% water and 25% solids </li></ul><ul><li>Diet lacking fiber = drier, compacted feces which can result in constipation </li></ul><ul><li>Sufficient fiber = Holds more water and is much softer which allows it to pass through easily </li></ul>
  56. 65. Quick Recap… <ul><li>Small Intestine: </li></ul><ul><ul><li>Breaks down food and absorbs nutrients </li></ul></ul><ul><ul><li>Villi increase’s surface area = more absorption </li></ul></ul><ul><ul><li>Moves the rest to the large intestine (through peristalsis) </li></ul></ul>
  57. 66. Quick Recap <ul><li>Large Intestine: </li></ul><ul><ul><li>Removes water </li></ul></ul><ul><ul><li>Moves undigested food (peristalsis) to be released as waste </li></ul></ul>
  58. 67. <ul><li>http://videos.howstuffworks.com/hsw/26494-managing-your-health-the-digestive-system-video.htm </li></ul>