6Teeth Structures crown neck root dentine external structureinternal structurecrowndentineneck- hard like bone but softer than enamelroot
7Teeth Structures crown neck root external structure internal structure - supply food & oxygen for growth & maintaining aliveneckblood capillariesnerve fibrespulp cavity(living tissues)root- produce sensation of pain when stimulated
8Teeth Structures crown neck root - anchor the tooth in its position external structureinternal structurecrowncementneckroot- anchor the tooth in its position
9Teeth Structures crown neck root - fibres attaching tooth to jawbone external structureinternal structurecrowngumneckPeriodontal membraneroot- fibres attaching tooth to jawbonejaw bone
10Two sets of teeth milk teeth permanent teeth no replacement for lost in young child before approximately six years oldwithout molar20 teethpermanent teethno replacement for lost32 teeth (including wisdom teeth)
12Dentition dental formula e.g. Human (permanent set) = 2123 2123 other dentitions :
13Tooth decay Causes: bacteria together with food remains, forming plaquebacteria produce acid which dissolves the enamel of toothacid penetrates into dentinebacteria infect pulp cavitycausing toothache
14Effect of Acid on a Tooth Investigation 7.1Effect of Acid on a Tooth
15dilute hydrochloric acid tooth covered with waxdilute hydrochloric acidprobingscrapingWhat 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.
16dilute hydrochloric acid scrapingprobingdilute hydrochloric acidtooth covered with waxDoes 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.
17Prevention 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
18Prevention of Tooth Decay use dental floss (to remove food remain between teeth)
19Prevention of Tooth Decay form a good tooth-cleaning habit by using dental disclosing agent
20Prevention of Tooth Decay brush our teeth at least twice a dayreplace your toothbrush when it wears outdo not bite hard materialshave a dental check-up at least once a year
21Movement of Food Mouth: Food chewed by teeth mixed with saliva to form bonus swallowed down the oesophagus through pharynxepiglottisoesophagustrachea[Note: Epiglottis (a piece of cartilage) covers the entrance to the trachea while swallowing to prevent food going down into lungs.]
25Because: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.)
26So,food pieces should be broken down into smaller pieces and then into substances with molecular size which is small enough to be absorbed
27Human Digestive System buccal cavitysalivary glandstonguetoothepiglottistracheaoesophagusdiaphragmcardiac sphincterliverstomachgall bladderspleenpancreaspyloric sphincterduodenumsmall intestineileumcolonlarge intestinecaecumappendixrectumanusHuman Digestive System
28Mechanical DigestionChewing : break down food into smaller pieces by teeth to increase the surface area for enzyme action (physical digestion)
29Chemical DigestionEnzymatic Reactions which digest food into simpler chemical forms
30Investigation 7.2To show the Differential Permeability of Dialysis Tubing to Starch & Glucose
31Starch-glucose mixture threadTest for glucoseTest for starchWhy 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.
32Starch-glucose mixture threadStarch-glucose mixtureTest for glucoseTest for starchWhich 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...
33Starch-glucose mixture threadStarch-glucose mixtureTest for glucoseTest for starchWhich 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.
34Starch-glucose mixture threadStarch-glucose mixtureTest for glucoseTest for starchWhich 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.
38Digestion in Buccal Cavity There are 3 pairs of salivary glandsSaliva contains water, mucus & enzyme (amylase)Water: moistens dry foodMucus: lubricates foodAmylase: digests about 5% of starch in mouth
39Action of Amylase on Starch Investigation 7.3Action of Amylase on Starch
40ABCthermometerwater bath at 37 ℃after 30 minuteseach test tubetest with Benedict’s solutiontest sample with iodine solutionWhat 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.
41ABCthermometereach test tubeafter 30 minutestest with Benedict’s solutionwater bath at 37 ℃test sample with iodine solutionWhat 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.
42ABCthermometereach test tubeafter 30 minutestest with Benedict’s solutionwater bath at 37 ℃test sample with iodine solutionWhat 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.
43Why is the temperature of the water bath set at 37 ℃ ? Cthermometereach test tubeafter 30 minutestest with Benedict’s solutionwater bath at 37℃test sample with iodine solutionWhy is the temperature of the water bath set at 37 ℃ ?Ans: Because enzymes work best at 37 ℃.
44What is the action of amylase on starch ? BCthermometereach test tubeafter 30 minutestest with Benedict’s solutionwater bath at 37 ℃test sample with iodine solutionWhat is the action of amylase on starch ?Ans: Amylase is an enzyme in saliva which helps to digest starch into maltose.
45What is the effect of boiling on amylase ? thermometereach test tubeafter 30 minutestest with Benedict’s solutionwater bath at 37 ℃test sample with iodine solutionWhat is the effect of boiling on amylase ?Ans: Amylase denatured after boiling.
46Chemical Digestionbreak down of starch molecules into maltose molecules by salivary amylase (from salivary glands)salivary glandsStarchmaltoses
47Stomach (Physical Digestion) Stomach Entrance: Cardiac SphincterStomach Exit: Pyloric SphincterRelaxation of cardiac sphincter & contraction of pyloric sphincter enable storage of food in stomach for a longer period of time
48Stomach (Physical Digestion) Squeezing & churning actions of stomach break down the partly digested food into smaller pieces which forms a semi-fluid called Chyme
49Stomach (Chemical Digestion) digestive juice : gastric juice (pH 2) (by gastric glands)enzymes : proteasebreak down of protein molecules into polypeptides or dipeptides
50Stomach (Chemical Digestion) hydrochloric acid :to provide acidic medium for maximum activity of enzymeto kill bacteriato stop the activity of salivary amylase(Stomach wall secretes a mucous layer to cover its inner surface: prevents autodigestion by protease)
51Small Intestine (mainly chemical digestion) Digestion of various food substances by several kinds of digestive juicesDigestive juices found in small intestine:1. Bile2. Pancreatic juice3. Intestinal juice
52Bile with bile salts (not an enzyme) produced in liver stored in gall bladderlivergall bladderduodenum
53Bile transport to duodenum through bile duct take action in duodenum bile pigment (excretory waste from breaking down of haemoglobin)livergall bladder
54Bile- contain bile salts which emulsify lipids into smaller droplets without chemical change ( ∴ NOT digest fats)- provide alkaline medium for enzymes to workoiloil droplets
55Effect of Bile Salt on Fat Investigation 7.4Effect of Bile Salt on Fat
5610 drops of bile salt solution 1cm3 of vegetative oilshakingobserve10 drops of bile salt solutionABWhat 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.
5710 drops of bile salt solution 1cm3 of vegetative oilshakingobserve10 drops of bile salt solutionABWhat is the action of bile salt on oil ?Ans: The bile salt reduces the surface tension of oil and emulsifies oil to droplets.
58Pancreatic Juice produced in pancreas action in duodenum Pancreas
59Pancreatic Juice - contain enzymes of 3 categories: 1. Carbohydrase (Amylase)2. Proteases3. Lipases- provide alkaline medium for enzymes to work
67Absorption 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
68Absorption of food in ileum It is long, with many finger-like villito provide large surface area for absorption of digested foodIt has thin wallto decrease the diffusion distance for easy diffusion of foodIt has well developed transport system (blood capillaries & lacteal)to maintain high concentration gradient for the diffusion of food
69Structure of a Villus blood capaillaries lacteal villi Epithelial cell venulearteriolelymph vessel
70Transverse Section of a villus showing food absorption glycerolnucleusfatty acidglucoseamino acidfatcapillarylactealMicro-villusepithelial cellTransverse Section of a villus showing food absorption
71Transportation 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
72Large intestine caecum & appendix no function in human (∴ small in size)colonabsorbs water & mineral saltsfailure to reabsorb water: Diarrhoearectumstores faeces temporarilyfor egestion (defaecation)coloncaecumappendixrectum
73Caecum & Appendix in Rabbit It is very large in size to store plant for long time for bacteria to secrete cellulase to digest cellulose to glucoseThe rabbit should re-ingest faeces for absorption of glucose ( ∵ absorption of food only proceeds in ileum)
76Egestion (Defaecation) removal of undigested or unabsorbed food substancesfaeces: semi-solid brown mass (includes undigested food, dead & live bacteria)faeces is temporarily stored in rectum & eventually be expelled through anus
77Assimilation diabetes a process which absorbs food incorporated as a part of body cellsdigested food is transported to liver by hepatic portal veinlacteal transports fat into lymph vessels & then into the bloodstreammalfunction of pancreas to secrete insulin: Diabetesdiabetes
78Functions of Liverchanges excess blood glucose to glycogen & stores in liver to regulate blood glucose leveldeaminates excess amino acidsto urea which is excreted by kidneyto glycogen for energy storage
79Functions of Liverstores vitamins A, D, E, K (which are fat soluble) iron & glycogenchanges Carotene to Vitamin Asecretes bile for fat emulsificationDetoxification:turns mild toxins into harmless substances