Chap6

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Chap6

  1. 2. The processes of nutrition ingestion digestion absorption assimilation egestion
  2. 3. Ingestion <ul><li>a process by which food is taken in through the mouth </li></ul><ul><li>a reflex action which is involuntary </li></ul><ul><li>it occurs when the food is put at the posterior position of the tongue </li></ul>
  3. 4. Teeth Structures external structure internal structure enamel dentine blood capillaries nerve fibres cement jaw bone gum crown neck root pulp cavity ( pulp tissues )
  4. 5. Teeth Structures <ul><li>outermost & hardest layer covering the crown ( 97% Ca, 3% organic matter ) </li></ul><ul><li>It is thickened and strengthened by food, saliva and drink </li></ul><ul><li>Fluoride ions increase its resistance to decay. </li></ul>external structure internal structure enamel crown neck root
  5. 6. Teeth Structures - hard like bone but softer than enamel ,living tissue, thread of cytoplasm are running through it. It is hardened by vitamin D external structure internal structure dentine crown neck root
  6. 7. Teeth Structures - supply food & oxygen for growth & maintaining alive - produce sensation of pain when stimulated external structure internal structure crown neck root blood capillaries nerve fibres pulp cavity ( living tissues )
  7. 8. Teeth Structures made up of connective tissues which make up your dentine and keep tooth alive. external structure internal structure crown neck root blood capillaries nerve fibres pulp cavity ( living tissues )
  8. 9. Teeth Structures <ul><li>In cement are embedded tuff fibers which pass into bone of jaw and anchor the tooth in its position </li></ul><ul><li>Bone covering the root </li></ul>external structure internal structure crown neck root cement
  9. 10. Teeth Structures - fibres attaching tooth to jawbone external structure internal structure gum crown neck root jaw bone Periodontal membrane
  10. 11. Two sets of teeth <ul><li>milk teeth </li></ul><ul><ul><li>in young child before approximately six years old </li></ul></ul><ul><ul><li>without molar </li></ul></ul><ul><ul><li>20 teeth </li></ul></ul><ul><li>permanent teeth </li></ul><ul><ul><li>no replacement for lost </li></ul></ul><ul><ul><li>32 teeth ( including wisdom teeth ) </li></ul></ul>
  11. 12. Types of teeth Types of Teeth Shape Functions Incisor Chisel-like & sharp Biting & cutting food Canine Pointed, curved & long Killing prey & tearing flesh Premolar & Molar 2 blunted points of cusps Crushing & grinding food
  12. 13. Dentition <ul><li>dental formula </li></ul><ul><li>e.g. Human (permanent set) = 2123 2123 </li></ul><ul><li>other dentitions : </li></ul>
  13. 14. Tooth decay <ul><li>bacteria together with food remains, </li></ul><ul><ul><li>forming plaque </li></ul></ul><ul><ul><ul><li>bacteria produce acid which dissolves the enamel of tooth </li></ul></ul></ul><ul><ul><ul><li>acid penetrates into dentine </li></ul></ul></ul><ul><ul><ul><li>bacteria infect pulp cavity </li></ul></ul></ul><ul><ul><ul><li>causing toothache </li></ul></ul></ul>Causes:
  14. 15. Diseases <ul><li>Dental decay (dental cavities) </li></ul><ul><li>Gum disease </li></ul>
  15. 16. Investigation 7.1 Effect of Acid on a Tooth
  16. 17. What do you find on the covered and uncovered parts of the tooth ? Ans: The acid dissolves the exposed enamel and leaves a small hole on the uncovered part, but holes do not appear on the covered part. tooth covered with wax dilute hydrochloric acid probing scraping
  17. 18. Does the acid take place in causing tooth decay ? Ans: Actually the acid produced by bacteria in the mouth is not very strong. Tooth decay is due to bad habits over a long period of time. tooth covered with wax dilute hydrochloric acid probing scraping
  18. 19. Prevention of Tooth Decay <ul><li>have a balanced diet (include Ca, P & vitamin D) </li></ul><ul><li>adding fluoride in water to strengthen the enamel of our teeth (NOT chlorine which kills bacteria in water) </li></ul><ul><li>avoid sugary food & drinks between meals </li></ul>
  19. 20. Prevention of Tooth Decay <ul><li>use dental floss (to remove food remain between teeth) </li></ul>
  20. 21. <ul><li>form a good tooth-cleaning habit by using dental disclosing agent </li></ul>Prevention of Tooth Decay
  21. 22. <ul><li>brush our teeth at least twice a day </li></ul><ul><li>replace your toothbrush when it wears out </li></ul><ul><li>do not bite hard materials </li></ul><ul><li>have a dental check-up at least once a year </li></ul>Prevention of Tooth Decay
  22. 23. Movement of Food <ul><li>Mouth: </li></ul><ul><li>Food chewed by teeth </li></ul><ul><li>mixed with saliva to form bonus </li></ul><ul><li> swallowed down the oesophagus through pharynx </li></ul>trachea epiglottis [Note: Epiglottis (a piece of cartilage) covers the entrance to the trachea while swallowing to prevent food going down into lungs.] oesophagus
  23. 24. Movement of Food <ul><li>Oesophagus: </li></ul><ul><li>Outer longitudinal & inner circular muscles contract & relax alternately ( peristalsis ) </li></ul><ul><li> Push food bolus to stomach </li></ul>muscle contraction muscle relaxation
  24. 25. A process by which large food molecules are broken down into smaller pieces Digestion
  25. 26. Why is digestion needed?
  26. 27. Because: food pieces and their molecules (e.g. starch, protein & fat) are usually too large to pass through the wall of our body for absorption (Note: Simple sugars, water, vitamins & minerals are small enough to be absorbed immediately.)
  27. 28. So, <ul><li>food pieces should be broken down into smaller pieces and then into substances with molecular size which is small enough to be absorbed </li></ul>
  28. 29. Human Digestive System salivary glands epiglottis oesophagus diaphragm cardiac sphincter stomach spleen pyloric sphincter colon caecum rectum anus large intestine pancreas buccal cavity tongue tooth trachea liver duodenum ileum appendix small intestine gall bladder
  29. 30. Mechanical Digestion Chewing : break down food into smaller pieces by teeth to increase the surface area for enzyme action ( physical digestion )
  30. 31. Chemical Digestion Enzymatic Reactions which digest food into simpler chemical forms
  31. 32. Investigation 7.2 To show the Differential Permeability of Dialysis Tubing to Starch & Glucose
  32. 33. Why is it necessary to rinse the dialysis tubing with tap water ? Ans: In order to remove any starch and glucose that may remain on the outside of the dialysis tubing. Starch-glucose mixture thread Test for glucose Test for starch
  33. 34. Which food substance is present in water surrounding the dialysis tubing 30 minutes after the beginning of the experiment ? Explain your answer. Ans: Glucose. As dialysis tubing is selectively permeable, starch molecules are too large to pass through the holes in the tubing... Starch-glucose mixture thread Test for glucose Test for starch
  34. 35. Which food substance is present in water surrounding the dialysis tubing 30 minutes after the beginning of the experiment ? Explain your answer. Ans: Only glucose molecules are small enough to pass through the dialysis tubing in this experiment. Starch-glucose mixture thread Test for glucose Test for starch
  35. 36. Which part of the body is presented by the dialysis tubing and the water in the boiling tube respectively ? Ans: Ileum and blood are represented by the dialysis tubing and water respectively. Starch-glucose mixture thread Test for glucose Test for starch
  36. 37. Where is food digested?
  37. 38. Sites where digestion occurs: Alimentary canal (gut) 1. Buccal cavity 2. Stomach 3. Small intestine
  38. 39. How is food digested in these sites?
  39. 40. Digestion in Buccal Cavity <ul><li>There are 3 pairs of salivary glands </li></ul><ul><li>Saliva contains water , mucus & enzyme (amylase) </li></ul><ul><li>Water: moistens dry food </li></ul><ul><li>Mucus: lubricates food </li></ul><ul><li>Amylase: digests about 5% of starch in mouth </li></ul>
  40. 41. Investigation 7.3 Action of Amylase on Starch
  41. 42. What are the results of the iodine test and Benedict’s test for tube A ? Ans: The result of iodine test is negative while the result of the Benedict’s test is positive. A B C thermometer water bath at 37 ℃ after 30 minutes each test tube test with Benedict’s solution test sample with iodine solution
  42. 43. What are the results of the iodine test and Benedict’s test for tube B ? Ans: The result of iodine test is positive while the result of the Benedict’s test is negative. A B C thermometer water bath at 37 ℃ after 30 minutes each test tube test with Benedict’s solution test sample with iodine solution
  43. 44. What are the results of the iodine test and Benedict’s test for tube C ? Ans: The result of iodine test is positive while the result of the Benedict’s test is negative. A B C thermometer water bath at 37 ℃ after 30 minutes each test tube test with Benedict’s solution test sample with iodine solution
  44. 45. Why is the temperature of the water bath set at 37 ℃ ? Ans: Because enzymes work best at 37 ℃ . A B C thermometer water bath at 37 ℃ after 30 minutes each test tube test with Benedict’s solution test sample with iodine solution
  45. 46. What is the action of amylase on starch ? Ans: Amylase is an enzyme in saliva which helps to digest starch into maltose. A B C thermometer water bath at 37 ℃ after 30 minutes each test tube test with Benedict’s solution test sample with iodine solution
  46. 47. What is the effect of boiling on amylase ? Ans: Amylase denatured after boiling. A B C thermometer water bath at 37 ℃ after 30 minutes each test tube test with Benedict’s solution test sample with iodine solution
  47. 48. Chemical Digestion break down of starch molecules into maltose molecules by salivary amylase (from salivary glands) Starch maltoses salivary glands
  48. 49. Stomach (Physical Digestion) Stomach Entrance: Cardiac Sphincter Stomach Exit: Pyloric Sphincter Relaxation of cardiac sphincter & contraction of pyloric sphincter enable storage of food in stomach for a longer period of time
  49. 50. Stomach (Physical Digestion) Squeezing & churning actions of stomach break down the partly digested food into smaller pieces which forms a semi-fluid called Chyme
  50. 51. <ul><li>digestive juice : gastric juice (pH 2) (by gastric glands) </li></ul><ul><li>enzymes : protease </li></ul><ul><li>break down of protein molecules into polypeptides or dipeptides </li></ul>Stomach (Chemical Digestion)
  51. 52. Stomach (Chemical Digestion) <ul><li>hydrochloric acid : </li></ul><ul><ul><li>to provide acidic medium for maximum activity of enzyme </li></ul></ul><ul><ul><li>to kill bacteria </li></ul></ul><ul><ul><li>to stop the activity of salivary amylase </li></ul></ul>(Stomach wall secretes a mucous layer to cover its inner surface: prevents autodigestion by protease )
  52. 53. Small Intestine (mainly chemical digestion) Digestion of various food substances by several kinds of digestive juices Digestive juices found in small intestine: 1. Bile 2. Pancreatic juice 3. Intestinal juice
  53. 54. Bile <ul><li>with bile salts (not an enzyme) </li></ul><ul><li>produced in liver </li></ul><ul><li>stored in gall bladder </li></ul>duodenum liver gall bladder
  54. 55. <ul><li>transport to duodenum through bile duct </li></ul><ul><li>take action in duodenum </li></ul><ul><li>bile pigment (excretory waste from breaking down of haemoglobin) </li></ul>liver gall bladder Bile
  55. 56. Bile - contain bile salts which emulsify lipids into smaller droplets without chemical change ( ∴ NOT digest fats) - provide alkaline medium for enzymes to work oil oil droplets
  56. 57. Investigation 7.4 Effect of Bile Salt on Fat
  57. 58. What happens to the mixtures in tubes A & B ? Ans: In tube A, bile salt emulsifies the vegetable oil to droplets. In tube B, the oil floats on top of water since oil and water do not mix well. 1cm 3 of vegetative oil shaking shaking observe observe 10 drops of bile salt solution A B
  58. 59. What is the action of bile salt on oil ? Ans: The bile salt reduces the surface tension of oil and emulsifies oil to droplets. 1cm 3 of vegetative oil shaking shaking observe observe 10 drops of bile salt solution A B
  59. 60. Pancreatic Juice <ul><li>produced in pancreas </li></ul><ul><li>action in duodenum </li></ul>Pancreas Duodenum
  60. 61. <ul><ul><li>Pancreatic Juice </li></ul></ul>- contain enzymes of 3 categories: 1. Carbohydrase ( Amylase ) 2. Proteases 3. Lipases - provide alkaline medium for enzymes to work
  61. 62. pancreatic amylase starch maltose starch maltose
  62. 63. pancreatic proteases protein Dipeptides/ polypeptides protein dipeptide protease
  63. 64. pancreatic lipases glycerol + 3 fatty acids lipid lipase glycerol fatty acids lipid
  64. 65. Intestinal Juice <ul><li>produced and take action in small intestine (duodenum & ileum) to complete the digestion of food </li></ul>Digestion in ileum ileum duodenum small intestine
  65. 66. Intestinal Juice - Contain enzymes of 2 categories: 1. Carbohydrase (eg. maltase ) 2. Protease
  66. 67. disaccharides (eg. maltose) monosaccharides (eg. glucose ) intestinal carbohydrase carbohydrase disaccharide monosaccharide
  67. 68. intestinal proteases dipeptides amino acids protease amino acid
  68. 69. Absorption <ul><li>stomach : absorbs alcohol & drugs </li></ul><ul><li>ileum : absorbs digested food (with a large amount of water) (∴ it absorbs the largest amount of water) </li></ul><ul><li>colon : absorbs water & mineral salts </li></ul>
  69. 70. <ul><li>It is long, with many finger-like villi </li></ul><ul><ul><li>to provide large surface area for absorption of digested food </li></ul></ul><ul><li>It has thin wall </li></ul><ul><ul><li>to decrease the diffusion distance for easy diffusion of food </li></ul></ul><ul><li>It has well developed transport system (blood capillaries & lacteal) </li></ul><ul><ul><li>to maintain high concentration gradient for the diffusion of food </li></ul></ul>Absorption of food in ileum
  70. 71. Structure of a Villus lacteal Epithelial cell arteriole venule blood capaillaries lymph vessel villi
  71. 72. Transverse Section of a villus showing food absorption glycerol nucleus fatty acid glucose amino acid fat capillary lacteal Micro-villus epithelial cell
  72. 73. Transportation of absorbed food in villi <ul><li>blood capillaries : absorb glucose & amino acids (which are smaller molecules) </li></ul><ul><li>lacteal : absorb fatty acids & glycerol (which are larger molecules) </li></ul><ul><ul><li>transport fats (glycerol & fatty acids recombine together after being absorbed) </li></ul></ul><ul><li>involve both diffusion & active transport </li></ul>
  73. 74. Large intestine <ul><li>caecum & appendix </li></ul><ul><ul><li>no function in human (∴ small in size) </li></ul></ul><ul><li>colon </li></ul><ul><ul><li>absorbs water & mineral salts </li></ul></ul><ul><ul><li>failure to reabsorb water: Diarrhoea </li></ul></ul><ul><li>rectum </li></ul><ul><ul><li>stores faeces temporarily </li></ul></ul><ul><ul><li>for egestion (defaecation) </li></ul></ul>caecum appendix colon rectum
  74. 75. Caecum & Appendix in Rabbit <ul><li>It is very large in size </li></ul><ul><ul><li> to store plant for long time </li></ul></ul><ul><ul><li> for bacteria to secrete cellulase </li></ul></ul><ul><ul><li> to digest cellulose to glucose </li></ul></ul>The rabbit should re-ingest faeces for absorption of glucose ( ∵ absorption of food only proceeds in ileum)
  75. 76. Digestive System in Rabbit
  76. 77. Alimentary canal of a rat
  77. 78. Egestion (Defaecation) <ul><li>removal of undigested or unabsorbed food substances </li></ul><ul><li>faeces: semi-solid brown mass (includes undigested food, dead & live bacteria) </li></ul><ul><li>faeces is temporarily stored in rectum & eventually be expelled through anus </li></ul>
  78. 79. Assimilation <ul><li>a process which absorbs food incorporated as a part of body cells </li></ul><ul><li>digested food is transported to liver by hepatic portal vein </li></ul><ul><li>lacteal transports fat into lymph vessels & then into the bloodstream </li></ul><ul><li>malfunction of pancreas to secrete insulin: Diabetes </li></ul>diabetes
  79. 80. Functions of Liver <ul><li>changes excess blood glucose to glycogen & stores in liver to regulate blood glucose level </li></ul><ul><li>deaminates excess amino acids </li></ul><ul><ul><li>to urea which is excreted by kidney </li></ul></ul><ul><ul><li>to glycogen for energy storage </li></ul></ul>
  80. 81. Functions of Liver <ul><li>stores vitamins A, D, E, K (which are fat soluble) iron & glycogen </li></ul><ul><li>changes Carotene to Vitamin A </li></ul><ul><li>secretes bile for fat emulsification </li></ul><ul><li>Detoxification : </li></ul><ul><li>turns mild toxins into harmless substances </li></ul>
  81. 82. ~ END ~

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