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The processes of nutrition ingestiondigestionabsorption assimilationegestion.

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Presentation on theme: "The processes of nutrition ingestiondigestionabsorption assimilationegestion."— Presentation transcript:

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3 The processes of nutrition ingestiondigestionabsorption assimilationegestion

4 Ingestion a process by which food is taken in through the mouth a reflex action which is involuntary it occurs when the food is put at the posterior position of the tongue

5 external structureinternal structure enamel dentine blood capillaries nerve fibres cement jaw bone gum crown neck root pulp cavity (pulp tissues) Teeth Structures

6 enamel crown neck root - outermost & hardest layer covering the crown (97% Ca, 3% organic matter) external structure Teeth Structures internal structure

7 dentine crown neck root - hard like bone but softer than enamel external structure Teeth Structures internal structure

8 crown neck root blood capillaries nerve fibres pulp cavity (living tissues) - supply food & oxygen for growth & maintaining alive - produce sensation of pain when stimulated external structure Teeth Structures internal structure

9 crown neck root - anchor the tooth in its position cement external structure Teeth Structures internal structure

10 Teeth Structures gum crown neck root jaw bone Periodontal membrane - fibres attaching tooth to jawbone external structureinternal structure

11 Two sets of teeth milk teeth –in young child before approximately six years old –without molar –20 teeth permanent teeth – –no replacement for lost – –32 teeth (including wisdom teeth)

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

13 Dentition dental formula e.g. Human (permanent set) = other dentitions :

14 Tooth decay bacteria together with food remains, –forming plaque bacteria produce acid which dissolves the enamel of tooth acid penetrates into dentine bacteria infect pulp cavity causing toothache Causes:

15 Effect of Acid on a Tooth

16 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 probingscraping

17 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 probingscraping

18 Prevention of Tooth Decay have a balanced diet (include Ca, P & vitamin D) adding fluoride in water to strengthen the enamel of our teeth (NOT chlorine which kills bacteria in water) avoid sugary food & drinks between meals

19 Prevention of Tooth Decay use dental floss (to remove food remain between teeth)

20 form a good tooth-cleaning habit by using dental disclosing agent Prevention of Tooth Decay

21 brush our teeth at least twice a day replace your toothbrush when it wears out do not bite hard materials have a dental check-up at least once a year Prevention of Tooth Decay

22 Movement of Food oesophagus trachea epiglottis Mouth: Food chewed by teeth mixed with saliva to form bonus swallowed down the oesophagus through pharynx [Note: Epiglottis (a piece of cartilage) covers the entrance to the trachea while swallowing to prevent food going down into lungs.]

23 Movement of Food muscle contraction muscle relaxation Oesophagus: Outer longitudinal & inner circular muscles contract & relax alternately (peristalsis) Push food bolus to stomach

24 A process by which large food molecules are broken down into smaller pieces

25 Why is digestion needed?

26 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 So, food pieces should be broken down into smaller pieces and then into substances with molecular size which is small enough to be absorbed

28 Human Digestive System salivary glands epiglottis oesophagus diaphragm cardiac sphincter stomach spleen pyloric sphincter colon caecum rectum anus large intestine pancreas buccal cavity tongue toothtrachea liver duodenum ileum appendix small intestine gall bladder

29 Mechanical Digestion Chewing : break down food into smaller pieces by teeth to increase the surface area for enzyme action (physical digestion)

30 Chemical Digestion Enzymatic Reactions which digest food into simpler chemical forms

31 To show the Differential Permeability of Dialysis Tubing to Starch & Glucose

32 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 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 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 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 Where is food digested?

37 Sites where digestion occurs: Alimentary canal (gut) 1. Buccal cavity 2. Stomach 3. Small intestine

38 How is food digested in these sites?

39 Digestion in Buccal Cavity There are 3 pairs of salivary glands Saliva contains water, mucus & enzyme (amylase) Water: moistens dry food Mucus: lubricates food Amylase: digests about 5% of starch in mouth

40 Action of Amylase on Starch

41 What are the results of the iodine test and Benedicts test for tube A ? Ans: The result of iodine test is negative while the result of the Benedicts test is positive. A BC thermometer water bath at 37 after 30 minutes each test tube test with Benedicts solution test sample with iodine solution

42 What are the results of the iodine test and Benedicts test for tube B ? Ans: The result of iodine test is positive while the result of the Benedicts test is negative. A BC thermometer water bath at 37 after 30 minutes each test tube test with Benedicts solution test sample with iodine solution

43 What are the results of the iodine test and Benedicts test for tube C ? Ans: The result of iodine test is positive while the result of the Benedicts test is negative. A BC thermometer water bath at 37 after 30 minutes each test tube test with Benedicts solution test sample with iodine solution

44 Why is the temperature of the water bath set at 37 ? Ans: Because enzymes work best at 37. A BC thermometer water bath at 37 after 30 minutes each test tube test with Benedicts solution test sample with iodine solution

45 What is the action of amylase on starch ? Ans: Amylase is an enzyme in saliva which helps to digest starch into maltose. A BC thermometer water bath at 37 after 30 minutes each test tube test with Benedicts solution test sample with iodine solution

46 What is the effect of boiling on amylase ? Ans: Amylase denatured after boiling. A BC thermometer water bath at 37 after 30 minutes each test tube test with Benedicts solution test sample with iodine solution

47 Chemical Digestion Chemical Digestion break down of starch molecules into maltose molecules by salivary amylase (from salivary glands) Starch maltoses salivary glands

48 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 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 digestive juice : gastric juice (pH 2) (by gastric glands) enzymes : protease break down of protein molecules into polypeptides or dipeptides Stomach (Chemical Digestion)

51 hydrochloric acid : – –to provide acidic medium for maximum activity of enzyme – –to kill bacteria – –to stop the activity of salivary amylase (Stomach wall secretes a mucous layer to cover its inner surface: prevents autodigestion by protease)

52 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 Bile with bile salts (not an enzyme) produced in liver stored in gall bladder duodenum liver gall bladder

54 transport to duodenum through bile duct take action in duodenum bile pigment (excretory waste from breaking down of haemoglobin) liver gall bladder Bile

55 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 Effect of Bile Salt on Fat

57 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 observe 10 drops of bile salt solution A B

58 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 observe 10 drops of bile salt solution A B

59 Pancreatic Juice produced in pancreas action in duodenum Pancreas Duodenum

60 Pancreatic Juice - contain enzymes of 3 categories: 1. Carbohydrase (Amylase) 2. Proteases 3. Lipases - provide alkaline medium for enzymes to work

61 pancreatic amylase starch maltose starch maltose

62 pancreatic proteases protein Dipeptides/ polypeptides protein dipeptide protease

63 pancreatic lipases glycerol + 3 fatty acids lipase glycerol fatty acids lipid

64 Intestinal Juice produced and take action in small intestine (duodenum & ileum) to complete the digestion of food ileum duodenum small intestine Digestion in ileum

65 Intestinal Juice - Contain enzymes of 2 categories: 1. Carbohydrase (eg. maltase) 2. Protease

66 disaccharides (eg. maltose) monosaccharides (eg. glucose) carbohydrase disaccharide intestinal carbohydrase monosaccharide

67 intestinal proteases dipeptidesamino acids protease amino acid

68 Absorption stomach : absorbs alcohol & drugs ileum : absorbs digested food (with a large amount of water) ( it absorbs the largest amount of water) colon : absorbs water & mineral salts

69 It is long, with many finger-like villi –to provide large surface area for absorption of digested food It has thin wall –to decrease the diffusion distance for easy diffusion of food It has well developed transport system (blood capillaries & lacteal) –to maintain high concentration gradient for the diffusion of food Absorption of food in ileum

70 lacteal Epithelial cell arteriole venule blood capaillaries lymph vessel villi Structure of a Villus

71 glycerol nucleus fatty acid glucose amino acid fat capillary lacteal Micro- villus epithelial cell Transverse Section of a villus showing food absorption

72 Transportation of absorbed food in villi blood capillaries : absorb glucose & amino acids (which are smaller molecules) lacteal : absorb fatty acids & glycerol (which are larger molecules) –transport fats (glycerol & fatty acids recombine together after being absorbed) involve both diffusion & active transport

73 Large intestine caecum & appendix –no function in human ( small in size) colon –absorbs water & mineral salts –failure to reabsorb water: Diarrhoea rectum –stores faeces temporarily –for egestion (defaecation) caecum appendix colon rectum

74 Caecum & Appendix in Rabbit It is very large in size to store plant for long time for bacteria to secrete cellulase to digest cellulose to glucose The rabbit should re-ingest faeces for absorption of glucose ( absorption of food only proceeds in ileum)

75 Digestive System in Rabbit

76 Alimentary canal of a rat

77 Egestion(Defaecation) removal of undigested or unabsorbed food substances faeces: semi-solid brown mass (includes undigested food, dead & live bacteria) faeces is temporarily stored in rectum & eventually be expelled through anus

78 Assimilation a process which absorbs food incorporated as a part of body cells digested food is transported to liver by hepatic portal vein lacteal transports fat into lymph vessels & then into the bloodstream malfunction of pancreas to secrete insulin: Diabetes diabetes

79 Functions of Liver changes excess blood glucose to glycogen & stores in liver to regulate blood glucose level deaminates excess amino acids – –to urea which is excreted by kidney – –to glycogen for energy storage

80 Functions of Liver stores vitamins A, D, E, K (which are fat soluble) iron & glycogen changes Carotene to Vitamin A secretes bile for fat emulsification Detoxification: turns mild toxins into harmless substances

81 ~ END ~ ~ END ~


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