Chap6-Power Point Viewer

8/8/2019 Chap6-Power Point Viewer

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The processes of nutritionThe processes of nutrition

ingestion digestion absorption

assimilationegestion


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IngestionIngestion

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 theposterior position of the tongue


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external structure internal structure

enamel

dentine

blood capillaries

nerve fibres

cement

jaw bone

gum

crown

neck

root

pulp cavity

(pulp tissues)

Teeth StructuresTeeth Structures


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enamelcrown

neck

root

- outermost & hardest layer

covering the crown (97% Ca,

3% organic matter)

- It is thickened and

strengthened by food, saliva

and drink

- Fluoride ions increase its

resistance to decay.

external structureTeeth StructuresTeeth Structures

internal structure


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dentinecrown

neck

root

- hard like bone but

softer than enamel

,living tissue, thread ofcytoplasm are running

through it. It is

hardened by vitamin D


internal structure


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crown

neck

root

blood capillaries

nerve fibres

pulp cavity(living tissues)

- supply food & oxygen for

growth & maintaining alive

- produce sensation

of pain when

stimulated


internal structure


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crown

neck

root

blood capillaries

nerve fibres

pulp cavity(living tissues)

made up of connective tissueswhich make up your dentine

and keep tooth alive.


internal structure


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crown

neck

root

- In cement are embedded

tuff fibers which pass into

bone of jaw and anchor thetooth in its position

- Bone covering the root

cement


internal structure


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Teeth StructuresTeeth Structures

gumcrown

neck

root

jaw bone

Periodontal membrane

- fibres attachingtooth to

jawbone

external structure internal structure


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Two sets of teethTwo 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)


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Types of teethTypes of teeth

Types of

TeethShape Functions

IncisorChisel-like &

sharp

Biting &

cutting food

Canine

Pointed,

curved &

long

Killing prey &

tearing flesh

Premolar

& Molar

2 blunted

points of

cusps

Crushing &

grinding food


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DentitionDentition dental formula

e.g. Human (permanent set) = 2123

2123 other dentitions :


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Tooth decayTooth 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:


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Diseases

Dental decay (dental

cavities)

Gum disease


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Effect of Acid on

a Tooth


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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 waxdilute hydrochloric acid

probingscraping


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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 waxdilute hydrochloric acid

probingscraping


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Prevention of Tooth DecayPrevention 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


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Prevention of Tooth DecayPrevention of Tooth Decay use dental floss (to remove food

remain between teeth)


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form a good tooth-cleaning habit by

using dental disclosing agent

Prevention of Tooth DecayPrevention of Tooth Decay


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Movement of FoodMovement of Food

oesophagustrachea

epiglottis

Mouth:

Food chewed by teeth

mixed with saliva to form bonus

swallowed down the oesophagusthrough pharynx

[Note: Epiglottis (a piece of cartilage) covers the

entrance to the trachea while swallowing to prevent

food going down into lungs.]


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Movement of FoodMovement of Food

muscle

contraction

muscle

relaxation

Oesophagus:

Outer longitudinal & inner

circular muscles contract &

relax alternately (peristalsis)

Push food bolus to stomach


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A process by which large food moleculesare broken down into smaller pieces


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Why is digestionWhy is digestionneeded?needed?


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Because: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.)


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So,So,

food pieces should be broken down

into smaller pieces and then into

substances with molecular size which

is small enough to be absorbed


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Human Digestive SystemHuman Digestive System

salivary

glandsepiglottis

oesophagus

diaphragm

cardiac sphincterstomachspleen

pyloric sphincter

coloncaecum

rectumanus

large

intestine

pancreas

buccal cavity

tongue

tooth

trachea

liver

duodenum

ileum

appendix

small

intestine

gall bladder


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Mechanical DigestionMechanical Digestion

Chewing : break down food into smallerpieces by teeth to increase

the surface area for enzyme

action (physical digestion)


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Chemical DigestionChemical Digestion

Enzymatic Reactions which digest

food into simpler chemical forms


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To show the Differential

Permeability of Dialysis Tubingto Starch & Glucose


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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

glucoseTest for

starch


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Which food substance is present in water surrounding the

dialysis tubing 30 minutes after the beginning of theexperiment ? 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

glucoseTest for

starch


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Which food substance is present in water surrounding the

dialysis tubing 30 minutes after the beginning of theexperiment ? 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

glucoseTest for

starch


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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

glucoseTest for

starch


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Where is foodWhere is fooddigested?digested?


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Sites where digestion occurs:Sites where digestion occurs:Alimentary canal (gut)

1. Buccalcavity

2. Stomach3. Small

intestine


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How is food digestedHow is food digestedin these sites?in these sites?


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Digestion in Buccal CavityDigestion 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


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Action of Amylase

on Starch


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What are the results of the iodine test and Benedicts testfor tube A ?

Ans: The result of iodine test is negative while the result

of the Benedicts test is positive.

A B Cthermometer

water bath

at 37

after 30 minutes

each test

tube

test with

Benedicts

solution

test sample

with iodinesolution


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What are the results of the iodine test and Benedicts testfor tube C ?

Ans: The result of iodine test is positive while the result of

the Benedicts test is negative.

A B Cthermometer

water bath

at 37

after 30 minutes

each test

tube

test with

Benedicts

solution

test sample

with iodinesolution


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Why is the temperature of the water bath set at 37 ?

Ans: Because enzymes work best at 37.

A B Cthermometer

water bath

at 37

after 30 minutes

each test

tube

test with

Benedicts

solution

test sample

with iodinesolution


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What is the action of amylase on starch ?

Ans:Amylase is an enzyme in saliva which helps to

digest starch into maltose.

A B Cthermometer

water bath

at 37

after 30 minutes

each test

tube

test with

Benedicts

solution

test sample

with iodinesolution


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Chemical DigestionChemical Digestionbreak down of starch molecules into

maltose molecules by salivary amylase

(from salivary glands)

Starch

maltoses

salivary glands


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StomachStomach

(Physical Digestion)(Physical Digestion)

Stomach Entrance: Cardiac Sphincter

Stomach Exit: Pyloric Sphincter

Relaxation of cardiac sphincter & contraction ofpyloric sphincter enable storage of food in

stomach for a longer period of time


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Stomach (Physical Digestion)Stomach (Physical Digestion)

Squeezing & churning

actions of stomach break

down the partly digested

food into smaller pieces

which forms a semi-fluid

called Chyme


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digestive juice : gastric juice (pH 2)

(by gastric glands) enzymes : protease

break down of protein molecules intopolypeptides or dipeptides

StomachStomach

(Chemical Digestion)(Chemical Digestion)


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StomachStomach

(Chemical Digestion)(Chemical Digestion)hydrochloric acid :

to provide acidic medium for

maximum activity of enzyme

to kill bacteria

to stop the activity of salivaryamylase(Stomach wall secretes a mucous layer to cover its inner

surface: prevents autodigestion by protease)


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Small IntestineSmall Intestine

(mainly chemical digestion)(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


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BileBile with bile salts (not an

enzyme)

produced in liver

stored in gall bladder

duodenum

livergall bladder


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transport to duodenum through bile duct

take action in duodenum

bile pigment (excretory waste from breakingdown of haemoglobin)

liver

gall bladder

BileBile


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BileBile- 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


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Effect of Bile Salt

on Fat


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What is the action of bile

salt on oil ?

Ans: The bile salt reduces

the surface tension of

oil and emulsifies oil to

droplets.

1cm3 of

vegetative

oil

shaking

shakingobserve

observe

10 drops of bile

salt solution

A

B


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Pancreatic JuicePancreatic Juice

produced in pancreas

action in duodenum

Pancreas

Duodenum


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Pancreatic JuicePancreatic Juice- contain enzymes of 3 categories:

1. Carbohydrase (Amylase)2. Proteases

3. Lipases

- provide alkaline medium forenzymes to work


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pancreatic amylasestarch maltose

starch maltose


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pancreaticproteasesprotein

Dipeptides/

polypeptides

protein

dipeptide

protease


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pancreatic lipasesglycerol + 3 fatty acids

lipase

glycerol

fatty acids

lipid

lipid


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Intestinal Juice

produced and take action in

small intestine (duodenum &

ileum) to complete the

digestion of food

ileum

duodenumsmall

intestine

Digestion in ileumDigestion in ileum


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Intestinal JuiceIntestinal Juice

- Contain enzymes of 2 categories:

1. Carbohydrase (eg. maltase)

2. Protease


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disaccharides

(eg. maltose)

monosaccharides

(eg. glucose)

carbohydrase

disaccharide

intestinalcarbohydrase

monosaccharide


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intestinalproteasesdipeptides amino acids

proteaseamino acid


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AbsorptionAbsorption

stomach : absorbs alcohol &

drugs

ileum : absorbs digested food(with a large amount of water)

( it absorbs the largest amount

of water)

colon : absorbs water & mineralsalts


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lacteal

Epithelial

cell

arteriole

venule

blood

capaillaries

lymph

vessel

villi

Structure of a VillusStructure of a Villus


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glycerol

nucleus

fatty acid

glucose

amino acid

fat

capillarylacteal

Micro-

villus

epithelial

cell

Transverse Section of a villus

showing food absorption


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Transportation of absorbedTransportation of absorbedfood in villifood 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 acidsrecombine together after being absorbed)

involve both diffusion & active transport


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Large intestineLarge 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


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Caecum & Appendix in RabbitCaecum & 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)


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Digestive System in RabbitDigestive System in Rabbit


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Alimentary canal of a rat


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EgestionEgestion

(Defaecation)(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


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AssimilationAssimilation

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


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Functions of LiverFunctions of Liver

changes excess blood glucose toglycogen & stores in liver to

regulate blood glucose level

deaminates excess amino acids

to ureawhich is excreted

by kidney

to glycogen for energy storage


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