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The processes of nutrition

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Presentation on theme: "The processes of nutrition"— Presentation transcript:

1

2 The processes of nutrition
ingestion digestion absorption egestion assimilation

3 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

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

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

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

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

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

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

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

11 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 Dentition dental formula e.g. Human (permanent set) = 2123 2123
other dentitions :

13 Tooth decay Causes: 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

14 Effect of Acid on a Tooth
Investigation 7.1 Effect of Acid on a Tooth

15 dilute hydrochloric acid
tooth covered with wax dilute hydrochloric acid probing scraping 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.

16 dilute hydrochloric acid
scraping probing dilute hydrochloric acid tooth covered with wax 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.

17 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

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

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

20 Prevention of Tooth Decay
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

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

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

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

24 Why is digestion needed?

25 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.)

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

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

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

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

30 Investigation 7.2 To show the Differential Permeability of Dialysis Tubing to Starch & Glucose

31 Starch-glucose mixture
thread Test for glucose Test for starch 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.

32 Starch-glucose mixture
thread Starch-glucose mixture Test for glucose Test for starch 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...

33 Starch-glucose mixture
thread Starch-glucose mixture Test for glucose Test for starch 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.

34 Starch-glucose mixture
thread Starch-glucose mixture Test for glucose Test for starch 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.

35 Where is food digested?

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

37 How is food digested in these sites?

38 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

39 Action of Amylase on Starch
Investigation 7.3 Action of Amylase on Starch

40 A B C thermometer water bath at 37 ℃ after 30 minutes each test tube test with Benedict’s solution test sample with iodine solution 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.

41 A B C thermometer each test tube after 30 minutes test with Benedict’s solution water bath at 37 ℃ test sample with iodine solution 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.

42 A B C thermometer each test tube after 30 minutes test with Benedict’s solution water bath at 37 ℃ test sample with iodine solution 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.

43 Why is the temperature of the water bath set at 37 ℃ ?
C thermometer each test tube after 30 minutes test with Benedict’s solution water bath at 37℃ test sample with iodine solution Why is the temperature of the water bath set at 37 ℃ ? Ans: Because enzymes work best at 37 ℃.

44 What is the action of amylase on starch ?
B C thermometer each test tube after 30 minutes test with Benedict’s solution water bath at 37 ℃ test sample with iodine solution What is the action of amylase on starch ? Ans: Amylase is an enzyme in saliva which helps to digest starch into maltose.

45 What is the effect of boiling on amylase ?
thermometer each test tube after 30 minutes test with Benedict’s solution water bath at 37 ℃ test sample with iodine solution What is the effect of boiling on amylase ? Ans: Amylase denatured after boiling.

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

47 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

48 Stomach (Physical Digestion)
Squeezing & churning actions of stomach break down the partly digested food into smaller pieces which forms a semi-fluid called Chyme

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

50 Stomach (Chemical Digestion)
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)

51 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

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

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

54 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

55 Effect of Bile Salt on Fat
Investigation 7.4 Effect of Bile Salt on Fat

56 10 drops of bile salt solution
1cm3 of vegetative oil shaking observe 10 drops of bile salt solution A B 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.

57 10 drops of bile salt solution
1cm3 of vegetative oil shaking observe 10 drops of bile salt solution A B What is the action of bile salt on oil ? Ans: The bile salt reduces the surface tension of oil and emulsifies oil to droplets.

58 Pancreatic Juice produced in pancreas action in duodenum Pancreas

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

60 pancreatic amylase starch maltose starch maltose

61 Dipeptides/ polypeptides protein
pancreatic proteases Dipeptides/ polypeptides protein protease dipeptide protein

62 glycerol + 3 fatty acids lipid pancreatic lipases lipid lipase

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

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

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

66 intestinal proteases dipeptides amino acids protease amino acid

67 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

68 Absorption of food in ileum
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

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

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

71 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

72 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) colon caecum appendix rectum

73 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)

74 Digestive System in Rabbit

75 Alimentary canal of a rat

76 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

77 Assimilation diabetes
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

78 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

79 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

80 ~ END ~


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