02. Nutrition in animals by Dilip Kumar Chandra
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Transcript of 02. Nutrition in animals by Dilip Kumar Chandra
By Dilip Kumar Chandra
The processes of nutritionThe processes of nutrition
ingestion digestion absorption
assimilationegestion
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 the posterior position of the tongue
Teeth StructuresTeeth Structures
gumcrown
neck
root
jaw bone
Periodontal membrane
- fibres attaching tooth to jawbone
external structure internal structure
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)
Types of teethTypes of teethTypes of
Teeth Shape Functions
Incissors Chisel-like & sharp
Biting & cutting food
Canine Pointed, curved & long
Killing prey & tearing flesh
Premolar & Molar
2 blunted points of
cusps
Crushing & grinding food
DentitionDentition dental formula
e.g. Human (permanent set) = 2123 2123
other dentitions :
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:
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
Movement of FoodMovement of FoodMouth:
Food chewed by teeth
mixed with saliva to form bonus
swallowed down the oesophagus through pharynx
oesophagustrachea
epiglottis
[Note: Epiglottis (a piece of cartilage) covers the entrance to the trachea while swallowing to prevent food going down into lungs.]
Movement of FoodMovement of FoodOesophagus:
Outer longitudinal & inner
circular muscles contract &
relax alternately (peristalsis)
Push food bolus to stomach
muscle contraction
muscle relaxation
A process by which large food molecules are broken down into smaller pieces
Why is digestion Why is digestion needed?needed?
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.)
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
Human Digestive SystemHuman Digestive System
salivary glandsepiglottis
oesophagusdiaphragmcardiac sphincter
stomachspleenpyloric sphincter
coloncaecum
rectumanus
large intestine
pancreas
buccal cavity
tongue
tooth
trachea
liver
duodenumileum
appendix
small intestine
gall bladder
Mechanical Mechanical DigestionDigestion
CHEWING : BREAK DOWN FOOD INTO SMALLER PIECES BY TEETH TO INCREASE THE SURFACE AREA FOR ENZYME ACTION (PHYSICAL DIGESTION)
Chemical DigestionChemical Digestion
Enzymatic Reactions which digest
food into simpler chemical forms
Sites where Sites where digestion occurs:digestion occurs:
Alimentary canal (gut)
1. Buccal cavity
2. Stomach3. Small
intestine
How is food digested How is food digested
in these sites?in these sites?
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
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 Cthermometer
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 B ?Ans: The result of iodine test is positive while the result of
the Benedict’s test is negative.
A B Cthermometer
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 C ?Ans: The result of iodine test is positive while the result of
the Benedict’s test is negative.
A B Cthermometer
water bath at 37 ℃
after 30 minutes
each test tube
test with Benedict’s
solution
test sample with iodine
solution
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 Benedict’s
solution
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.
A B Cthermometer
water bath at 37 ℃
after 30 minutes
each test tube
test with Benedict’s
solution
test sample with iodine
solution
What is the effect of boiling on amylase ?
Ans: Amylase denatured after boiling.
A B Cthermometer
water bath at 37 ℃
after 30 minutes
each test tube
test with Benedict’s
solution
test sample with iodine
solution
Chemical Chemical DigestionDigestionBREAK DOWN OF STARCH MOLECULES INTO MALTOSE MOLECULES BY SALIVARY AMYLASE (FROM SALIVARY GLANDS)
Starch
maltoses
salivary glands
Stomach Stomach (Physical Digestion) (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
Stomach (Physical Stomach (Physical Digestion) Digestion)
SQUEEZING & CHURNING ACTIONS OF STOMACH BREAK DOWN THE PARTLY DIGESTED FOOD INTO SMALLER PIECES WHICH FORMS A SEMI-FLUID CALLED CHYME
• DIGESTIVE JUICE : GASTRIC JUICE (PH 2) (BY GASTRIC GLANDS)
• ENZYMES : PROTEASE
• BREAK DOWN OF PROTEIN MOLECULES INTO POLYPEPTIDES OR DIPEPTIDES
Stomach Stomach (Chemical Digestion)(Chemical Digestion)
Stomach Stomach (Chemical Digestion)(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)
Small Intestine Small Intestine (mainly chemical (mainly chemical digestion)digestion)
DIGESTION OF VARIOUS FOOD SUBSTANCES BY SEVERAL
KINDS OF DIGESTIVE JUICES
Digestive juices found in small intestine:
1. Bile2. Pancreatic juice3. Intestinal juice
BileBile• with bile salts (not an
enzyme)• produced in liver• stored in gall bladder
duodenum
livergall bladder
• transport to duodenum through bile duct• take action in duodenum• bile pigment (excretory waste from breaking
down of haemoglobin)
liver
gall bladder
BileBile
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
Effect of Bile Salt on Fat
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.
1cm3 of vegetative
oil
shaking
shakingobserve
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.
1cm3 of vegetative
oil
shaking
shakingobserve
observe
10 drops of bile salt solution
A
B
Pancreatic JuicePancreatic Juice
• produced in pancreas
• action in duodenum
Pancreas
Duodenum
Pancreatic JuicePancreatic Juice
- contain enzymes of 3 categories: 1. Carbohydrase (Amylase) 2. Proteases 3. Lipases- provide alkaline medium for
enzymes to work
pancreatic amylasestarch maltose
starch maltose
pancreatic proteases
proteinDipeptides/ polypeptides
protein
dipeptide
protease
pancreatic lipases glycerol + 3 fatty acids
lipase
glycerol
fatty acids
lipidlipid
Intestinal Juice• produced and take action in
small intestine (duodenum & ileum) to complete the digestion of food
ileumduodenum
smallintestine
Digestion in ileumDigestion in ileum
Intestinal JuiceIntestinal Juice- Contain enzymes of 2 categories:
1. Carbohydrase (eg. maltase)
2. Protease
disaccharides(eg. maltose)
monosaccharides(eg. glucose)
carbohydrasedisaccharide
intestinal carbohydrase
monosaccharide
intestinal proteases
dipeptides amino acids
proteaseamino acid
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 & mineral salts
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 Absorption of food in ileumin ileum
lactealEpithelial cell
arteriole
venule
blood capaillaries
lymph vessel
villi
Structure of a VillusStructure of a Villus
glycerol
nucleusfatty acid
glucose
amino acid fat
capillarylacteal
Micro-villus
epithelial cell
Transverse Section of a villus showing food absorption
Transportation of absorbed Transportation of absorbed food 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 acids recombine together after being absorbed)
involve both diffusion & active transport
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)
caecumappendix
colon
rectum
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