1. TOPIC 53 Animal Nutrition
5.1 Diet
5.2 Human Alimentary Canal
5.3 Mechanical and Physical Digestion
5.4 Chemical Digestion
5.5 Absorption and Assimilation
Use the following to check what you can do,
ffick one of the columns for each criterial
o Define balanced diet
. List the different classes of food that make a balanced diet
List the chemical elements which make up carbohydrates, fats and
proteins
. State the importance of protein, carbohydrates and fats in our diet
State the importance of taking Vitamins C and D, minerals (calcium &
iron) and fibre in our diet
Give the sources for carbohydrates, proteins, fats, vitamins C and D
and mineralsalts (iron and calcium)
Explain the relation between diet and age, diet and sex and diet and
activity of an individual
. Deflne malnutrition
. Explain constipation and the problems associated with this condition
. Explain obesity and the health problems associated with this condition
Name and state the function of the parts of the system that make up the
human alimentary canal and the associated oroans
. Define ingestion, digestion, absorption, assimilation and egestion
To identify which part of the alimentary canat is involved in the process
mentioned above
tdentiff the different types of teeth and state their functions in relation to
tooth structure
r State the process and causes of tooth decay
. State ways to prevent tooth decay
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- Chp 5 Animal Nutrition Page I of2l
2. Describe the proper care of teeth
. Describe chewing
. Describemechanicaldigestion
r Describe the process of peristalsis
. Definechemicaldigestion
r Distinguish chemical digestion and mechanical digestion
Describe the role of salivary and pancreatic amylase and maltase in fire
State the end-products f-or the digestion of starch
. Describe the functions of pepsin and lipase
. State the end products for digestion of proteins and fats
. State the optimum pH for these enzymes
. Describe how the digested food molecules are aGorbed in the bbol
o State the roles of liver in the digestion and assimilation of food
Explain what happens to excess glucose
Explain what happens to excess amino acids
. Explain wtrat happens to excess fats
Describe briefly how and in what form, exces@
the bodv
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3. 5,2 HUMAN ALIMENTARY GANAL
* TIre food we eat goes through five different processes in our body:
(1) lngestion: taking food into the body (eating).
(2t Digestion:the breaking down of large complex food molecules into simple, soluble molecules.
(3) Absorption: digested food from the alimentary canal diffuses into the blood stream.
(4) Assimilation: the use of absorbed food to form new cells or part of cells.
(5) Egestion: passing out undigested food as faeces.
* 1yre atimentary canal is the canal (tube) along which food passes to be processed.
,/ Assimilation does not take place in the alimentary canal'
./ The human alimentary canalis about 900cm (9 m) long.
I The canal is able to fit into our bodies because it is folded into loops.
rt
Diagram below shows the human alimentary canal and the organs associated with it (shaded)
tongue mouth re-rttlrj
salivary gland
windpipe
oesophagus
I
diaphragm
eal bladder
liver
stornach Ft-**l
duodenum pancreas
small f
intestine
I ileum
colon
large
intestine
fectum
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4. Parts of the Human Alimentary Ganal and the Associated orqans
(a) Mouth
lngestion takes place in the mouth
Physical digestion starts here
(when teeth break the food into smaller pieces and the tongue rollthe food to mix it with saliva)
Chemical digestion of starch starts in the mouth (saliva contains enzyme salivary amylase to
break down starch to maltose)
1uy Oesophaqus:
r. It is a tube through which food is transferred from the mouth to the stomach.
This tube is muscular; it contractsand relaxes to push the food to the stomach. The contraction
and relaxation of the muscular oesophagus is called peristalsis.
(c) Stomach:
muscular bag-like structure which stores ingested food for a few hours.
It is a
- proteins and fats remains in the stomach for about 2 to 3 hours
- carbohydrates remains in the stomach for only one hour
Glands in the wall of the stomach produce gastric juices containing hydrochloric acid and
enzyme pepsin.
Protein is digested in the stomach.
(d) Liver:
Produces bile. Bile does not contain any enzymes
^
Bile breaks down bigger fat molecules to smaller fat molecules
^
(e) Gall bladder:
Gall bladder is connected to liver.
^
The bile produced by the liver is temporarily stored in the gall bladder
^ The bile is then released to the duodenum (first part of the small intestine) when it is needed.
^
(0 Pancreas
^ Secretes pancreatic juice enzymesduodenum.
A Pancreatic juice contains
into the
for the digestion of carbohydrates, fats and proteins
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5. 1s; Small intestine:
A lt is about 6 metres long and consists of duodenum and ileum.
(i) Duodenum:
F First part of small intestine where acidic food from stomach is neutralized by the bile juice
(released from gall bladde$ and mix with pancreatic juice (released from pancreas)
F Bile not only neutralise the acidic food, it also helps to break down fats to smaller molecules.
Pancreatic juice contain enzymes to break down proteins, carbohydrates and fats
(ii) Ileum:
digestion of food.
the walls of ileum
th; Larqe intestine:
lt is about 1.5 metres long and consists of colon and rectum.
^
(i) Colon:
F lt absorbs water and minerals from undigested food.
(ii) Rectum:
F A short muscular tube which stores faeces before egestion.
(i) Anus:
An opening through which the faeces is passed out.
^
LSC-201 l_C.S.Biology - Chp 5_Animal Nutrition Pagel? o{21
6. 5.3 MECHANICAL AND PHYSICAL DIGESTION
Digestion
Digestion is the breaking down of large complex foods into smaller simpler food units.
m We must digest our food so that lt is small enough to pass through the thin walls of the ileum into the blood.
m There are two types oi digestion:
(1) Physicaldigestion
(2) Chemicaldigestion.
Physical Digestion
Physical digestion breaks down food into smatler pieces. lt is sometimes called
mechanical digestion. This type of digestion does not chemically change the food.
Chewing
+ Example of physical digestion is chewing in our mouth with our teeth.
3E ffre functions of teeth are to cut, tear and grind food into smaller pieces.
ffi tt is important to chew our food because:
(a) it breaks the food up into smatler pieces that are easier to swallow.
(b) it makes digestion by enzymes easier. when food has been broken up into smaller pieces,
there
is a larger surface area for the enzymes to act on.
(c) chewing allows the food to be mixed with the saliva. Saliva also contains mucus which helps
food to move easily along the alimentary canal.
+ There are fourdifferent types of teeth:
(1) incisor
(2) canine
(3) premolar
(4) molar
Each type has a different shape, size and function.
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7. The table below shows the four types of teeth in humans
T5,pe of tooth Description Function
.
fl-*Itr*
y urcrsor .
chisel-shaped
narrow bitine surface cutting food
ff- pointed r chisel-shaped and pointed cutting and
.
y canine narrow biting surface tearing food
(e)-- curp a three blunt cusps crushing and
premolar a broad biting surface grinding food
W
-ai- broad r four blunt cusps crushing and
r
hl 3sil:"" morar broad biting surface grinding food
Dental Decav
+ Teeth have a very hard outer layer to protect them while chewing food.
+ Over time this hard layer can be dissotved away by acid produced by bacteria in the
mouth.
$ This is called dental decay or tooth decay.
S The acid is produced when bacteria digest leftover food stuck in between the teeth.
S Too much sweet food and not cleaning the teeth properly will cause tooth decay to happen
more
quickly.
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Chp Animal Nutrition Page 14 of2l
8. The diagram below shows the stages in the decay of a molar tooth
* sugar-r-acid
1. bactcria
the (ur the
(in
mouth) foo$
NO PATN SLICT{T
TOOTHAC}IE
bone-like
inner
region
acid attacks the hard surface acid eats through the innner
of the tooth, forming a cavity region
SEVERE AGONY!
TOoftIActm
inntrmost region
containing ncrv!s painful
4, acid reaches the innermost swelling
rqgion, where it attacks the 5. decay reachs base of tooth
nerve$ and causs a painful swelling
The Proper Care of Teeth
+ You can have strong, healthy teeth by doing the following:
(1) Keep your teeth clean
,/ You should brush your teeth at teast twice a day, early in the morning and before going to bed.
./ lf possible, brush your teeth after every meal or at least rinse your mouth with water to remove
any food remains on your teeth.
,/ Food particles that are trapped between your teeth are best removed with a piece of dental floss.
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9. ,/ lt is better to use fluoride toothpaste when brushing your teeth. Fluoride hardens the tooth
surface making it more resistant to tooth decay.
(21 Eat less sweet and stickY food
,/ lf sugar is present in your mouth for too long, your teeth will start to decay.
(3) Visit the dentist regularly
./ Do not wait to visit your dentist until you get a toothache.
Peristalsis
The walls of the whole alimentary canal consist of layers of muscles and cells which secrete slimy liquid
^ called mucus,
a The layers of muscles bring about wave-like contractions called peristalsis which push food along the
alimentary canal.
.r The slimy mucus makes it easier for the food to move along.
Below shows peristalsis - wave-like contractions which move food along the alimentary canal
*lE Muscle
contracts
Food Muscle
relaxes
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10. 5.4 CHEMICAL DIGESTION
Chemicaldigestion is a process by which complex food molecules are broken down into
simple soluble substances. Enzymes are used to produce these chemical changes.
Most of the food we ingest is insoluble and made up of molecules that are too large and complex to pass
through the wall of the small intestine (ileum) into the blood vessels.
Below shows digestion reduces complex food substances into simple units
oooo oo
ooo
digestion oo o
glucose units
B f a
E
- ".!
digcsrion
w
nm
amino acid units
F
n
rt- %
cligestion
tfn
tf
Fats farry acids and glycerol
f ln most animals, digestion is extracellular.
(Extracellular means that digestion takes ptace outside the body cells. ln most animals, digestion
takes place in ihe alimentary canal.)
* Example of extracellular digestions are:
salivarv amvlase
Stomach: protein pepsn
(b) > polypeptide (peptones)
(c) Duodenum: fats bile (no enzyme)
, emulsified fats
oancreatic amvlase
(d) lteum: maltose maltase , glucose
polypeptide (peptones) peptidase , amino acids
frts &'"e r fatty acids and glycerol
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