Biology Form 4 Textbook (DLP)

• Saliva contains salivary amylase that hydrolyses starch to maltose.
• The pH of the saliva ranges between 6.5–7.5, which is suitable for salivary amylase to act at its

optimum.

Salivary amylase
Starch + water maltose the muscular
oweaslolspohfatghues
Saliva helps food to form bolus and makes it easier oesophagus
contract

to be swallowed. When swallowing, the epiglottis
will close the trachea opening to prevent food from
entering the trachea. In the oesophagus, the food
bolus is moved by peristalsis.
thwealmlsuosfctuhlear
Peristalsis is the rhythmic contraction and relaxation oesophagus bolus
of muscles along the alimentary canal. Peristalsis
relax FIGURE 9.2 Peristalsis

pushes the bolus through the oesophagus until it Brainstorm!
enters the stomach (Figure 9.2). Chew slowly a
small piece of
Digestion of protein in the bread. Observe
stomach the taste when
you first started
The surface of the stomach wall is lined with epithelial chewing and after CHAPTER 9
cells that have undergone adaptations in structure a few minutes of
and function to form gastric glands (Figure 9.3). chewing. Is there
These epithelial cells are chief cells, parietal cells any difference in the
and mucous cells. taste of the bread?
• Chief cells secrete pepsinogen.
• Parietal cells secrete hydrochloric acid.
• Mucous cells secrete mucus.

oesophagus gastric gland

stomach

epithelium

duodenum

sphincter

FIGURE 9.3 Structure of stomach and gastric mucous
gland tissues cells
parietal
Pmeupksoisnaogen is an inactive enzyme that is activated cells
by hydrochloric acid to become pepsin. Pepsin then chief
hydrolyses proteins into polypeptides. cells

pepsin polypeptides 145
submukosParotein + water

9.2.3

The functions of hydrochloric acid are to: The food in the stomach is mixed with gastric
(a) prepare a medium with a suitable pH (pH juice made up of hydrochloric acid and pepsin.
Food is churned by the peristaltic action of
1.5–2.0) for pepsin to act the stomach wall muscles for a few hours.
(b) stop the enzymatic action of salivary The contents in the stomach finally change to
a semifluid called chyme. Chyme enters the
amylase duodenum slowly when the sphincter muscle
(c) kill bacteria in food relaxes.
The function of mucus is to protect the stomach
wall from the reaction of hydrochloric acid and
digestive enzymes.

Digestions of carbohydrates, proteins and lipids in the
small intestine

The small intestine consists of duodenum, jejunum and ileum. Duodenum is the first part of the
small intestine which receives chyme from the stomach. Duodenum also receives bile produced by
the liver and pancreatic juice secreted by the pancreas (Figure 9.4).

PANCREAS liver stomach
bile duct
The pancreas secretes
pancreatic amylase, trypsin
and lipase into the duodenum
through the pancreatic duct.

LIVER gallbladder chyme
pancreas
• Produces bile
duodenum
• The gallbladder stores bile.
pancreatic duct
• The bile flows into the
duodenum through the bile FIGURE 9.4 Components that are involved
duct. in digestion that take place in the small
intestine
• Functions of bile
DUODENUM
– neutralise the acidic
chyme • Pancreatic amylase hydrolyses starch to maltose
Starch + water pancreatic amylase maltose
– prepare an alkali
condition (pH 7.6–8.6) • Trypsin hydrolyses polypeptides into shorter peptides.
for enzyme action in the Polypeptide + water trypsin
duodenum peptides

– emulsify lipids by • Lipase hydrolyses lipids into fatty acids and glycerols.
breaking down lipids into Lipid + water lipase fatty acid and glycerol
tiny droplets to increase
surface area for lipase
activity.

146 9.2.4

Glands on the ileum wall secrete mucus and intestinal juice that contains
maltase, sucrase, lactase, lipase and erepsin. The alkali medium in the
ileum allows enzymes to act at its optimum.

CARBOHYDRATE DIGESTION LIPID DIGESTION ICT 9.1

• Maltase hydrolyses maltose into Lipase hydrolyses lipids Video: Processes of digestion,
glucose. absorption and defaecation
into fatty acids and (Accessed on 21 August 2019)
Maltose + water maltase glucose
glycerols. Across the fields
• Sucrase hydrolyses sucrose into
glucose and fructose. Lipid lipase Fatty acids Chemical digestion
involves enzyme-
Sucrose + water sucrase glucose + + water + glycerol catalysed hydrolysis
fructose reaction. For example,
PROTEIN DIGESTION an enzyme is needed
• Lactase hydrolyses lactose into in the decomposition
glucose and galactose. Erepsin hydrolyses of starch into glucose.
peptides into amino acids.
Lactose + water lactase glucose +
galactose Peptides erepsin amino

+ water acids

1.2 9.1ActivistyeitivitcA Studying the digestion of starch in a Experiment
food sample

Problem statement tthhetehrrmemromomomemteeetrter CHAPTER 9
What is the effect of amylase on starch? AAA B BB

AB

Hypothesis 3ossuofmo3ssls0uuofpl.mt5sl0ieouop%l.nft5nieoso1%nfain%os1mnai%osym+ntlaasy3+rstlcaaem3hrscelmh l s3oufm3sosdufplimssdeotpliinfsleols1teinfil%dols1eniw%dos+natwast3+eratcartm3hercrlmh l
Amylase hydrolyses starch to a reducing sugar.
w(3aw7w(3teaa°7rtCtee°b)rCrabt)bhaathth
Variables (37 °C)

Manipulated: Presence of amylase

Responding: Presence of reducing sugar

Fixed: Temperature of water bath at 37˚C,
concentration of starch suspension and volume of mixture

Materials
0.5% amylase solution, 1% starch suspension, iodine solution, Benedict’s solution and distilled water

Apparatus
Tripod stand, Bunsen burner, wire gauze, 500 ml beaker, test tube holder, thermometer, stopwatch,

test tube, dropper, glass rod and measuring cylinder

9.2.5 147

Procedure
1 Label 2 test tubes as A and B.

2 Add 3 ml of 1% starch suspension to each test tube.

3 Fill test tube A with 3 ml of 0.5% amylase solution and test tube B with 3 ml of distilled water.

4 Soak both test tubes in a water bath with a temperature of 37 °C for 10 minutes.

5 After 10 minutes, remove 2 ml of the solution from test tube A and put it into a different test
tube. Add 3 drops of Benedict’s solution to that test tube and heat the test tube in a boiling
water bath for 1 minute. Record the colour of the content.

6 Add 2 drops of iodine solution to the remainder of test tube A. Observe and record the colour
of the contents.

7 Repeat steps 5 and 6 for test tube B.

Results Contents Iodine test Benedict’s test
Test tube
A 1% starch suspension + 0.5% amylase
solution

B 1% starch suspension + distilled water

Discussion
1 Explain the reaction that occurs in test tube A.

2 What is the purpose of preparing test tube B?

Conclusion
Is the hypothesis accepted? Suggest a suitable conclusion for this experiment.

Activity 9.2 Studying digestion of protein in a food Experiment
sample

Problem statement
What is the effect of pepsin on protein?

Hypothesis
Pepsin hydrolyses proteins in the albumen suspension into polypeptides.

Variables
Manipulated: Presence of pepsin
Responding: Clarity or turbidity of mixture after 20 minutes.
Fixed: Temperature at 37˚C, concentration of pepsin solution and dilute hydrochloric acid

Materials
Albumen suspension (egg white), 1% pepsin solution, distilled water and 0.1 M dilute hydrochloric

acid

Apparatus
Test tube, measuring cylinder, 500 ml beaker, water bath at 37 °C, dropper, thermometer and

stopwatch.

148

9.2.5

Procedure thermometer
1 Prepare an apparatus set-up as follows. AB
Test tube A: 5 ml of albumen suspension + 1 ml of 0.1 M hydrochloric
water bath
acid + 1 ml 1% pepsin solution (37 °C)

Test tube B: 5 ml of albumenAsuspensBion + 1 ml of 0.1 M hydrochloric
acid + 1 ml distilled water

2 Soak all test tubes in a water bath at 37 °C.
3 Observe the condition of mixtures in test tubes A and B at the beginning

of the experiment and after 20 minutes.

Results

Test tube 0 minute Clarity or turbidity
20 minute

A

B

Discussion
1 Explain the results achieved in test tube A and B.

2 What is the purpose of adding hydrochloric acid into each test tube?

Conclusion
Is the hypothesis accepted? Suggest a suitable conclusion for this experiment.

CHAPTER 9

Activity 9.3 Studying the digestion of lipids in a food Experiment
sample

Problem statement
What is the effect of lipase on lipid?

Hypothesis
Lipase hydrolyses lipids into fatty acids and glycerols.

Variables
Manipulated: Presence of lipase
Responding: Time taken for the phenolphthalein indicator to turn from pink to colourless
Fixed: Temperature at 37°C, volume of cooking oil and combined volume

Materials
Cooking oil, 0.2 M sodium carbonate solution, dishwashing liquid, phenolphthalein indicator, distilled

water and lipase

9.2.5 149

Apparatus
Two test tubes, test tube rack, water bath at 37 °C, 5 ml and 1 ml syringes, dropper, stopper and
stopwatch

Procedure thermometer
1 Prepare two test tubes aAnd label tBhem as A and B. AB

2 Fill each test tube A and B with the following:

• 2 ml of cooking oil water bath
• 1 ml of 0.2 M sodium carbonate solution (37 °C)
• 1 ml of dishwashing liquid
3 Close both test tubes with stoppers. Shake both test tubes
vigorously after adding the dishwashing liquid.

4 Add 3 drops of phenolphthalein indicator to each test tube and
shake the test tube.

5 Add 1 ml of lipase into test tube A and 1 ml of distilled water into test tube B.

6 Soak both test tubes in a water bath at 37°C.

7 Record the time taken for the phenolphthalein indicator to turn from pink to colourless.

Results

Test tube Contents Time taken for the phenolphthalein indicator to turn
from pink to colourless (minute)

A 1 ml of lipase

B 1 ml of distilled water

Discussion
1 Why is a phenolphthalein indicator used in this experiment?
2 What is the purpose of adding dishwashing liquid into each test tube?
3 Explain the reaction that happens in test tube A.
4 Explain the results obtained in test tube B.

Conclusion
Is the hypothesis accepted? State the suitable conclusion for this experiment.

9.1Formative Practice 4 The small intestine secretes a few types of
enzymes to complete the digestion process.
1 Explain the importance of the digestion Explain how these enzymes complete the
process for humans. digestion process.

2 Name the structures in the alimentary canal
that are involved in food digestion.

3 Name the main cells in the gastric glands
and explain the functions of these cells.

150 9.2.5

9.3 Absorption
The adaptations of ileum and villus in the
absorption of digested food
Simple molecules produced from the digested food are absorbed in the ileum
of the small intestine.

ILEUM ileum CHAPTER 9
cross section of a small
The long ileum is adapted
to absorb nutrients intestine
because its internal layer
is folded and covered by villus
tiny projections called
villi (singular: villus) (Figure 9.5). lacteal
epithelial cells
VILLUS (PLURAL: VILLI) blood capillaries

Villus has the following lymph vessel
adaptations to absorb nutrients
(Figure 9.5): microvillus nucleus
• The epithelial layer of the basement
membrane
villus is one cell thick. This helps
accelerate nutrient absorption. mucus
• Goblet cells secrete mucus to aid goblet
digestion. cells
• The network of blood capillaries helps
to transport digestive products to the FIGURE 9.5 Adaptations of ileum and villi
whole body. to absorb digested food.
• Lacteal carries droplets of fatty acids and
glycerol. 151
• The intestinal glands secrete intestinal
juices that have digestive enzymes.

MICROVILLUS

On the surface of the villus
epithelium, there are many
tiny projections called
microvillus. Microvillus
provides a large surface
area to increase the rate of
nutrient absorption (Figure 9.5).

9.3.1 9.3.2

Absorption of digested food is summarised in Figure 9.6 and Table 9.1.

Petunjuk:
Glukosa

ICT 9.2 Indicator: Asid amino

Video: View inside the laLacktteeaall GlucAosidselemak
small intestine
(Accessed on 21 Giserol
August 2019)
Amino acids

Titisan halus lipid

FattGyaalacktiodssa

MMilillelennnnilaaaclltCeCaaalrererer Fruktosa

A gastroenterologist Glycerol
is a medical specialist
who specialises in blood cKaappiillalarirdiaersah Lipid droplets
the human digestive Galactose
system.
Fructose

FIGURE 9.6 Absorption of digested food

blood capillaries TABLE 9.1 Method of food absorption in the ileum
Activity Zone
Digested food Absorbed Methods of
Gather information through absorption
about the
absorption of Fructose Facilitated diffusion
alcohol and drugs.
Glucose and galactose Epithelial cells Active transport
Amino acids into blood Active transport
Vitamins B and C capillaries Absorbed with water

Water Osmosis

Fatty acids and glycerols Simple diffusion
recombine through the
condensation process to Epithelial cells
form tiny droplets of lipids into lacteal
in the epithelial cells

Vitamins A, D, E, K Simple diffusion
dissolve in the lipid

9.2Formative Practice 3 Explain the adaptations of the small intestine
to increase the surface area for absorption of
1 Name the main structures for the absorption nutrients.
of digested food.
4 Explain how the following substances can be
2 Name the structure in the villus involved in transported across the plasma membrane.
the transporting of the following nutrients:
(a) Glucose, galactose and amino acids
(a) amino acids (b) Fatty acids and glycerol

(b) vitamins A and E

152 9.3.2

9.4 Assimilation CHAPTER 9

Biological Lens The role of the circulatory system

Liver cirrhosis The human circulatory system consists of the blood circulation system
is a type of liver and the lymphatic system to help transport nutrients to be assimilated.
disease caused In the assimilation process that occurs in cells, nutrients are used to form
by factors such as complex compounds or structures of components. The blood capillaries
alcoholic drinks, in the small intestine combine to form the hepatic portal vein that
toxic substances transports blood to the liver.
and hepatitis. Liver Lacteals combine to form bigger lymph vessels in the lymphatic system.
cells are replaced Then, the contents of the lymph vessels enter the thoracic duct that
by scarred cells flows into the left subclavian vein. This lipid is then transported by
that can cause blood throughout the body.
failure in the liver
functions. Hepatitis Functions of liver in the assimilation of
is an inflammation digested food
of the liver caused
by viral infection, The liver is the regulator that controls the quantity of nutrients that
toxic substances enter the blood circulatory system. The liver carries out the following
or autoimmune functions.
reaction
(Photograph 9.1). METABOLISM OF DIGESTED FOOD
• Glucose is used for cellular respiration. Amino acids are used for
Activity Zone
Conduct a research synthesising plasma proteins and enzymes.
on the various • Through the deamination process, excess amino acids are turned
functions of the
liver and produce a into urea to be excreted through the urine.
scrap book
DETOXIFICATION
• Liver cells expel toxic substances from the blood.
• Toxic substances are expelled through the urine.

STORAGE OF NUTRIENTS
Excess glucose is converted to glycogen to be stored.

PHOTOGRAPH 9.1 Normal Normal liver Liver of a cirrhosis
liver and liver of a cirrhosis patient
patient
153
9.4.1 9.4.2

ASSIMILATION PROCESS IN THE LIVER

AMINO ACIDS GLUCOSE

• The liver synthesises plasma protein and • Glucose in the liver is used for cellular respiration
enzymes from amino acids. when required by the body and the excess is
converted to glycogen and stored in the liver.
• Excess amino acids cannot be stored in
the body and are broken down through the • When the glucose level in the blood decreases and
deamination process to form urea which is the body needs energy, glycogen is converted to
then expelled. glucose.

• When the glucose supply is insufficient, the • When the glycogen supply reaches a maximum
liver converts amino acids into glucose. level, the excess glucose is converted to fats.

liver cellular respiration body cell

excess aacmliidinso excess synthesis of synthesis of plasma
glycogen plasma proteins protoplasm membrane
is stored and enzymes (in the cell) synthesis

glucose urea

excreted by
hepatic the kidneys
portal vein

glucose amino acid lipid

small fatty acids + glycerol FIGURE 9.7 Transportation of nutrients and
intestines the assimilation in the liver and cells

carbohydrates protein lipid

ASSIMILATION PROCESS IN CELLS

AMINO ACIDS GLUCOSE LIPIDS

• Amino acids are used • Glucose is oxidised through • Lipids such as phospholipid
to synthesise new cellular respiration to release and cholesterol are the primary
protoplasm and also energy, water and carbon components that build the plasma
repair damaged dioxide. membrane.
tissues.
• Excess glucose is kept as • Excess fats are kept in adipose
• Amino acids are used to glycogen in muscles. tissues found underneath the skin
synthesise hormones as stored energy.
and enzymes. • Energy is used for cell
processes such as protein • Fat is oxidised to release energy
synthesis. when there is insufficient glucose.

9.3Formative Practice I understand the difference between

1 State the meaning of assimilation.

2 Explain the functions of the liver in the assimilation of digested food.

154 9.4.2

9.5 Defaecation

Biological Lens Functions of the large
intestine
The large intestine
has a huge population After the absorption of nutrients is
of bacteria. There completed in the ileum, undigested food,
are more than 1000 dead cells, epithelial cells, fibre and water
different species of enter the large intestine and move slowly
bacteria in the large through peristaltic action. Fibre consists
intestine and a healthy of cellulose walls of plant cells. The large
balance between •in taesbtsionrepctaiornrieosf owuattetwr o main functions:
beneficial and less
beneficial bacteria and vitamins
is very important for • formation of faeces colon
health and a stable
environment in the
alimentary canal.

ABSORPTION OF WATER AND VITAMINS caecum rectum CHAPTER 9
appendix anus
Substances absorbed are
• water and mineral salts FIGURE 9.8 Large intestines
• metabolic byproducts of some bacteria such

as vitamin B, vitamin K and folic acid.

FORMATION OF FAECES

• After the water is absorbed, the remaining waste is a semisolid called faeces. Faeces
contains dead cells from the inner layer of the intestine, waste products such as bile
pigments, bacteria and toxic substances.

• The walls of the large intestine secrete mucus to smoothen the movement of faeces until the
anus. The movement of faeces takes about 12 to 24 hours before entering the rectum.

• The faeces will accumulate in the rectum until the pressure in the rectum increases and
triggers the need to expel faeces from the body.

• The rectum muscles will contract to expel faeces from the anus. This process is called
defaecation.

Brainstorm! 9.4Formative Practice 3 Explain the importance
of water absorption and
What is the effect 1 State the main function of the vitamins in the large intestine.
of antibiotics large intestine.
on the large 4 Explain the formation process
intestine’s bacterial 2 What are the substances of faeces.
population? absorbed in the large
intestine?

9.5.1 155

9.6 Balanced Diet

Biological Lens Energy value in a food sample

A balanced diet refers to a diet that consists of all seven food classes
(carbohydrates, lipids, proteins, vitamins, mineral salts, fibre and water)
in the correct proportion and balanced quantity according to individual
needs so that optimal health can be maintained.

1 calorie (cal) = 4.2 joule (J) ENERGY VALUE

1 kilojoule = 1000 joule • Energy value is the total amount of energy released when one
gram of food is oxidised completely.
Across the fields
• The energy value in food is measured in the form of heat energy,
4.2 J g-1 °C-1 refers that is, in kilojoule per gram (kJ g-1).
to the specific heat
capacity of water, • Another unit of heat energy is calorie.
that is, the energy
required to increase • 1 calorie or 4.2 joule is defined as the quantity of heat energy
the temperature of 1 g needed to raise the temperature of 1 gram water by
of water by 1 °C. 1 degree Celsius (°C) at a pressure of 1 standard atmosphere.

• Energy value of food (kJ g-1)

= Water mass (g) × 4.2 J g-1 °C-1 × Increase in water temperature (°C)

Mass of food sample (g) × 1000

sAecit1iv.2itycA9.4 Studying the energy value of food samples Experiment

Problem statement cotton barrier
Which food sample has the highest energy value? wool
thermometer
Hypothesis boiling tube
Groundnuts have a higher energy value compared to
cashew nuts. distilled
water
Variables food sample
Manipulated: Types of food samples needle
Responding: Energy value of food sample
Fixed: Water mass plasticine

Materials retort
Distilled water, food samples (cashew nuts and groundnuts), stand

cotton wool and plasticine

Apparatus
Retort stand with a clamp, thermometer, boiling tube,

long needle, electronic weighing scale, barrier, measuring

cylinder and Bunsen burner

156 9.6.1

Procedure
1 Weigh a cashew nut using an electronic weighing scale and record its mass.

2 Measure 20 ml of distilled water using a measuring cylinder and pour it into a boiling tube.

3 Clamp the boiling tube to the retort stand and put in the thermometer.

4 Fix the position of the thermometer using cotton wool.

5 Record the initial temperature of the distilled water.

6 Stick the cashew nut on the needle and hold the needle upright using plasticine.

7 Place the barrier around the apparatus set-up.

8 Light the cashew nut using a Bunsen burner and place it below the boiling tube.

9 Stir the water in the boiling tube slowly and record its highest temperature after the cashew nut
has completely burned.

10 Replace the water in the boiling tube.

11 Repeat steps 1 to 9 using groundnuts.

12 Calculate the energy value for each food sample using the following formula:

Energy value of = Water mass (g) × 4.2 J g-1 °C–1 × Increase in water temperature (°C)
food (kJ g–1)
Food sample mass (g) × 1000

13 Record your results in the table below.

Results

Food Food Initial Final Increase of Energy value CHAPTER 9
sample sample temperature temperature Temperature of food
mass (g) of water (°C) (kJ g–1)
of water (°C)
(°C)

Cashew nuts

Groundnuts

Discussion
1 Which food sample shows the highest energy value?

2 State two precautionary steps for this experiment.

3 Compare the energy value of food samples obtained from this experiment with their theoretical
energy values. Are there any differences? If yes, explain why.

Conclusion
Is the hypothesis accepted? Suggest a suitable conclusion for this experiment.

The contents of vitamin C in fruit or vegetables juices

The nutrient content in various types of food is different. For example, the vitamin C
content in fruits and vegetables are different.

9.6.2 157

1.2 9.5AcsteivitiitvyitcA Determining the contents of vitamin C in fruit juice Experiment
and vegetable juice.

Problem statement
Which fruit juice or vegetable juice has the highest content of vitamin C?

Hypothesis
Orange juice has the highest content of vitamin C compared to lime juice and carrot juice.

Variables
Manipulated: Types of fruit and vegetable juices
Response: Volume of fruit juice or vegetable juice needed to decolourise DCPIP solution
Fixed: Concentration of DCPIP solution and concentration of an ascorbic acid solution

Materials
Orange juice, lime juice and fresh carrot juice, 0.1% ascorbic acid solution, 1% DCPIP solution and

distilled water

Apparatus
Syringe needles (1 ml and 5 ml), knife, 50 ml beaker, specimen tube, juicer and sieve

Procedure
1 Put 1 ml of 1% DCPIP solution in a specimen tube.

2 Fill the 5 ml syringe needle with a 0.1% ascorbic acid solution. ascorbic acid
Ensure that there are no air bubbles trapped in it.
specimen tube
3 Insert the tip of the syringe needle into the specimen tube and drip
ascorbic acid drop by drop into the DCPIP solution while stirring
slowly until the blue colour of the DCPIP solution is decolourised.

4 Record the volume of the 0.1% ascorbic acid solution needed to DCPIP solution
decolourise the blue colour of the DCPIP solution.

5 Repeat steps 1 to 4 twice to get the average volume for each
different juice.

6 Record the volume of each juice in the table below.

7 Calculate the concentration of vitamin C of each juice using the following formula.

Percentage of vitamin C = volume of ascorbic acid solution × 0.1%
volume of juice used

Vitamin C concentration (mg ml-1) = volume of ascorbic acid solution × 1.0%
volume of juice used

Results Volume of solution/juice Vitamin C Vitamin C concentration
required to decolourise DCPIP concentration (mg ml-1)
Solution / Juice 0.1
solution (ml) (%)
0.1% ascorbic
acid solution 123 Average
Orange juice
Lime juice
Carrot juice

158 9.6.2

Discussion
1 Which juice has the highest content of vitamin C?

2 Why is a 0.1% ascorbic acid solution used as the standard?

Conclusion
Is the hypothesis accepted? Suggest a suitable conclusion for this experiment.

One of the factors that affect the loss of vitamin C content is temperature. Therefore, fruit or
vegetables must be kept at a suitable temperature range to preserve vitamin C.

1.2 9.6ActivisteyitivitcSAtudying the effect of temperature on vitamin C in Experiment
orange juice

Problem statement
What is the most suitable ambient temperature to keep orange juice?

Hypothesis
Orange juice stored at a low ambient temperature has the highest content of vitamin C.

Variables Take Note! CHAPTER 9
Manipulated: Ambient temperature
Responding: Volume of orange juice required to decolourise DCPIP solution Ensure that
Fixed: Volume of DCPIP solution the juice is not
exposed too long
Materials to avoid oxidation.
Oranges, 1% DCPIP solution and ice

Apparatus
Specimen tube, knife, syringe needles (1 ml and 5 ml), beakers (50 ml and 100 ml),

Bunsen burner, tripod stand, sieve and wire gauze

Procedure
1 Prepare 60 ml of orange juice.

2 Label the beakers A, B and C. Pour 20 ml of orange juice into each beaker.

3 Soak beaker A in ice, leave beaker B at room temperature and soak beaker C in boiling water
for 30 minutes.

4 After 30 minutes, determine the vitamin C content in the orange juice as shown in Activity 9.5.

5 Calculate the concentration of vitamin C in the orange juice at each different temperature.

Results
Record your results in an appropriate table.

9.6.2 159

Discussion
1 Is there a difference in the vitamin C content for the juice at different temperatures?
2 What is the effect of temperature on vitamin C in the orange juice?
3 Based on the results, suggest the best way to ensure that you get a high content of vitamin C

from fruit juice or vegetable juice.

Conclusion
Is the hypothesis accepted? Suggest a suitable conclusion for this experiment.

PHOTOGRAPH 9.2 Diet modifications for specific individuals
A sample serving based on
Pinggan Sihat Malaysia A balanced diet for each individual will vary according to lifestyle,
health conditions and specific nutritional requirements. Each
MMilillelennnniaall CCaarererer individual must make wise choices based on a nutrition guide.
For example, suggestions for nutritional needs can be made based
Nutritionists are on Pinggan Sihat Malaysia. Pinggan Sihat Malaysia illustrates
specialists in the the relative quantity of various food classes in a balanced diet
field of nutrition (Photograph 9.2).
who advise Excessive food intake that is rich in saturated fats can cause health
specific individuals problems such as obesity and cardiovascular diseases.
on suitable diets.
The cause of obesity

Obesity is caused by the storage of excess fats as a result of
imbalanced food intake and use of energy.

Effects of obesity

Individuals who are obese need to reduce the intake of carbohydrates
and fats as well as increase the intake of vegetables and fruits.
Otherwise, a diet with excessive saturated fats and high cholesterol
may cause diabetes mellitus and various cardiovascular diseases such
as atherosclerosis and hypertension which may result in heart attacks
(myocardial infarction) or stroke if not treated.

Activity Zone Cancer patients who are undergoing cancer treatment, need to modify
their diet to ensure they receive sufficient energy, reduce the risk of
Plan meals based infections and enable quick recovery.
on Pinggan Sihat
Malaysia for different
individuals such as
obese individuals,
cancer patients and
heart patients.

160 9.6.3

9.7 Health Issues Related to the
Digestive System and Eating
Habits

Adaptation of digestive organs

duodenum Obesity is a health issue on the rise throughout the world. Although
jejunum obesity can be controlled through diet management and routine
exercise programmes, at times, obesity requires medical treatment.
Specialist doctors may suggest surgical procedures to reduce body
weight such as gastric bypass (Figure 9.9). A gastric bypass involves a
reduction of the stomach size using various methods of surgery.
Among the short-term side effects of this surgery are acid reflux,
nausea, vomiting, expanded oesophagus, certain food prohibitions
and risk of infection. The long-term side effects are dizziness, low
blood sugar level, malnutrition, stomach ulcer and defaecation
problems.

gastric

sac Health issues related to defaecation

Part of the The food class that is most important in the defaecation process CHAPTER 9
stomach is fibre. Intake of diet that is high in fibre such as fruits and
that has vegetables can smoothen bowel movements. This can prevent
been health problems such as constipation, colon cancer, rectum cancer
bypassed and haemorrhoid.

jejunum Some of the functions of fibre are to:
• stimulate peristalsis
Part of the • absorb and expel toxic substances
duodenum • regulate the absorption of glucose especially for diabetes
that has been
bypassed mellitus patients
• increase the population of beneficial bacteria in the large
food
intestine
digestive juice
Besides, the intake of a large amount of water can ensure that the
FIGURE 9.9 Gastric bypass faeces stay soft and move easily along the large intestine to aid the
process of defaecation.

9.7.1 9.7.2 161

Health issues related to eating habits

Apart from a balanced diet, eating habits also play an important role in fulfilling our energy
requirements and maintaining our health. Poor eating habits and an imbalanced diet can
cause numerous health problems such as gastritis, muscle dysmorphia, anorexia nervosa and
bulimia nervosa.

ANOREXIA
NERVOSA

GASTRITIS Anorexia
Gastritis refers to the nervosa is
quite common
inflammation and corrosion of amongst
the stomach epithelial layer teenage
by gastric juice when there girls who are
is no food in the stomach. obsessed with
Untreated gastritis can result their body weight.
in gastric ulcers. The causes Anorexics will avoid
of gastritis include eating food to achieve their
irregular quantities of food at ideal body weight. They also
irregular hours and excessive suffer from psychological problems
intake of alcohol or painkillers. and nutrient deficiency because of their
normal digestive system is affected.

BULIMIA NERVOSA MUSCLE
DYSMORPHIA
For people with bulimia
nervosa who are also Some individuals
obsessed with controlling feel that their size
their body weight, they is small with not
will eat a lot and vomit out enough growth.
the food that they have So, they subject
eaten or take laxatives that themselves
cause diarrhoea. In the long to extreme
run, the patient may suffer from weightlifting
dehydration, nutritional problems and training and exercise.
eventually cardiovascular disease or kidney failure. Sometimes, they consume
steroids or muscle building
supplements. This health issue is called
muscle dysmorphia.

Activity Zone 9.5Formative Practice 2 Predict the effect of
modifying digestive organs
Do a case study about 1 In your opinion, why is fibre such as gastric bypass on
the following health issues important in the defaecation human health.
related eating habits: process. Explain your
• diabetes type 2 answer. 9.7.3
• obesity
• acid reflux
• pica

162

Summary

NUTRITION AND THE HUMAN DIGESTIVE SYSTEM

Digestive System Balanced Diet Health Issues Related to the
Digestive System and Eating
• Digestion • Energy value
• Absorption • Contents of vitamin C in Habits
• Assimilation
• Defaecation fruit or vegetables juices • The effects of modifying
• Diet modifications for digestive organs on human
health
specific individuals
• Health issues related to
defaecation

• Health issues related to eating
habits

Self Reflection CHAPTER 9

Have you mastered the following important concepts?
• Structure of the human digestive system
• Mechanism of digestion
• Process and products of carbohydrate digestion in the mouth
• Process and products of protein digestion in the stomach
• Digestions of carbohydrates, proteins and lipids in the small intestine
• Adaptations of ileum and villus in the absorption of digested food
• Assimilation of digested food and liver functions
• Defaecation
• Balanced diet and energy value in food samples
• Diet modifications for specific individuals
• Health issues related to the digestive system and eating habits

163

Summative Practice 9

1 Some people cannot drink milk because it causes diarrhoea and a bloated stomach. Explain
why.

2 Amin had some meat dishes for lunch. Explain how the protein is digested in Amin’s
stomach.

3 An individual has the following eating habits:
Overeating in a short period of time followed by intentional throwing
up on purpose after each meal.

Explain how this eating habit can affect the health of this individual.
4 Figure 1 shows the alimentary canal in humans.

Z
XY

FIGURE 1
(a) Name structures X and Y.
(b) (i) The enzymes in X are only effective in an alkaline environment. Explain how an

alkaline environment is maintained in X.
(ii) Explain how Y is involved in the digestion of carbohydrates in X.
(c) Name the enzyme found in Z. Explain how this enzyme functions in the digestion of

proteins.
(d) A student enjoys eating a lot of oranges. Explain the effect of eating too many oranges

on the digestion of starch in X.

164

Essay Questions

5 Explain the processes that fat molecules undergo starting from the duodenum until it is
finally used by body cells.

6 A teenager had the following for his breakfast.

Buttered bread – 2 pieces Fresh milk – 1 glass
Hard-boiled eggs – 2 Apple – 1


Explain what happens to the final digested products of his breakfast in his body cells.

7 (a) Explain why a diet rich in fats is not good for health.

(b) Suggest suitable types of food for someone who wants to reduce weight and reduce
the risk of contracting cardiovascular disease. Explain your answer.

(c) Explain the processes of starch digestion, absorption and assimilation in the human
body.

Enrichment CHAPTER 9

8 Medicines in the form of capsules are not broken down in the stomach but absorbed easily
by the small intestine. When the blood sample of the patient is taken and analysed, it is
found that the molecular structure of this medicine is different from its original molecular
structure. Explain why.

9 How are drinks with added artificial sweeteners produced and marketed?

10 Nowadays, many individuals prefer ready-to-eat or frozen food products due to their busy
lifestyles. Predict the health risks that may arise if these foods are taken continuously for a
long period of time and in large quantities.

Complete answers are
available by scanning the
QR code provided

165

CHAPTER

Transport in
Humans and

10 Animals

What is a Do you KNOW...
mechanical heart?
••• crHHbeWiroltocouhwwuoranldatddttaoocoisreierersyscsutusthtehlhyaeefestlcoutlheyoirdmeymmsas?ppriytnhosptantoueteimmctnhts?pesybbostllfooetoomhdde?
• ltWyomhthpaethaahtruiecmtshayenshtceeimraclsuth?laitsosruyeasnrdelated

166

10.1 Types of Circulatory System 10.4 Mechanism of Blood Clotting
10.4.1 Justify the necessity for blood
10.1.1 Justify the necessity of transport clotting mechanism.
systems in complex multicellular 10.4.2 Describe blood clotting
organisms. mechanism.
10.4.3 Describe health issues related to
10.1.2 Identify substances that are blood clotting: • thrombosis
transported by the transport • embolism • haemophilia
system: • substances required by
a cell • waste products of a cell 10.5 Blood Groups of Humans
10.5.1 Describe ABO blood group.
10.1.3 Conceptualise types of circulatory 10.5.2 Correlate ABO blood group with
system in complex multicellular blood donation.
organisms. 10.5.3 Describe the Rhesus factor.
• open circulatory system 10.5.4 Reason out the incompatibility of
• closed circulatory system Rhesus factor in pregnancies.

10.1.4 Compare and contrast circulatory 10.6 Health Issues Related to the Human
systems in complex multicellular Circulatory System
organisms: • insects
• fish • amphibians • humans 10.6.1 Justify the necessity for a healthy
circulatory system.
10.2 Circulatory System of Humans
10.6.2 Communicate about
10.2.1 Describe components of the cardiovascular diseases.
human circulatory system:
10.7 Lymphatic System of Humans
• heart • blood vessel • blood 10.7.1 Synthesise the process of
10.2.2 Explain the composition of blood: formation of tissue fluid and lymph.
10.7.2 Compare and contrast the
• blood plasma • blood cells contents of lymph and:
10.2.3 Compare and contrast the types of • tissue fluid • blood
10.7.3 Describe components of the
blood vessels: lymphatic system: • lymph
• artery • vein • capillary • lymphatic capillaries
10.2.4 Label the structure of a human • lymphatic vessels• lymph nodes
heart and associated blood • lymphatic organs
vessels: • aorta • vena cava 10.7.4 Justify the necessity of the
• pulmonary artery and pulmonary lymphatic system:
vein • complements the blood
• coronary artery and coronary circulatory system
vein. • transports lipid-soluble
• semilunar valve substances
• bicuspid valve and tricuspid • body defence
valve • septum
10.2.5 Describe the functions of parts of 10.8 Health Issues Related to the Human
the heart. Lymphatic System

10.3 Mechanism of Heartbeat 10.8.1 Describe health issues related to
the lymphatic system.
10.3.1 Describe the human heartbeat
mechanism: 167
• sinoatrial node (pacemaker)
• atrioventricular node
• bundle of His • Purkinje fibres

10.3.2 Communicate about forces that
cause the blood to circulate in
humans: • pumping of the heart
• contraction of skeletal muscles

10.1 Types of Circulatory System
The necessity for transport systems in
complex multicellular organisms
Each living cell requires essential substances such as oxygen and
Substance nutrients, and expels cellular waste products such as carbon dioxide
exchange can occur and nitrogenous wastes.
by diffusion because In Chapter 2, you learned how unicellular organisms such as Amoeba sp.
the cells are in the get their essentials and expel wastes by diffusion from and to its external
environment. surroundings. Unicellular organisms have a small body mass. Therefore,
the total surface area to volume ratio (TSA/V) of the organism is large.
As such, Amoeba sp. does not require a specialised transport system to
transport substances in and out of the cell.
What about multicellular organisms? Can multicellular organisms
obtain all essential substances and expel wastes by simple diffusion like
unicellular organisms?
Large complex multicellular organisms cannot obtain essential
substances and expel wastes by diffusion because their TSA/V is small.
The distance between the external environment and the cell is too far for
direct substance exchange. So, how do complex multicellular organisms
get essential substances for their cells?

external environment Substance
is far away from cells exchange cannot
epidermis occur by diffusion
because the
external environment cells are too far
away from the
environment.

body cells

FIGURE 10.2 Substance
exchange for multicellular
organisms

FIGURE 10.1 Substance 10.1.1 10.1.2
exchange for unicellular

168 organisms

To address this problem, multicellular organisms have an internal ICT 10.1
transportation system. In vertebrates, the transportation system is
called the blood circulatory system. Activity: Studying the effects of
Before studying further the blood circulatory system, conduct an changes in total surface area
experiment to study the effects of changes in TSA/V on the diffusion to volume ratio (TSA/V) on the
rate.
diffusion rate.
Types of circulatory systems in multicellular
organisms

The circulatory system in multicellular organisms is divided into two
types: open circulatory system and closed circulatory system.

OPEN CIRCULATORY SYSTEM CLOSED CIRCULATORY SYSTEM
• In an open circulatory system, • In a closed circulatory system, blood is

haemolymph flows directly into the always contained in a continuous closed
body cavity (haemocoel) and bathes the blood vessel and is distributed to the
cells. whole body.
• Haemolymph is a blood-like nutritious • The exchange of substances that are
liquid found in most invertebrates such essential to cells such as oxygen and
as insects and molluscs. nutrients occurs across the walls of
blood capillaries.

haheamemolyomlymphphvevsesseslel blobolododvevsesseslel CHAPTER 10
haheamemocooceolel
blobolodod blobolododcacpailplailrlayry
haheamemolyomlymphph
hehaerat rt hehaerat rt

ceclleslls ceclleslls
opoepne-ne-nedneddedvevsesseslel

10.1.3 169

OPEN CIRCULATORY SYSTEM CIRCULATORY SYSTEM

Circulatory System of Insects Circulatory System of Fish

• The circulatory system of insects is • The heart of the fish has two chambers,
an open circulatory system. This that is, an atrium (plural: atria) and a
means that one or more hearts pump ventricle.
haemolymph through the blood vessels
into the haemocoel. • Blood that leaves the ventricle is pumped
to the gill capillaries to enable gaseous
• Haemolymph flows out from the heart exchange.
into the haemocoel when the heart
contracts. • The gill capillaries carry blood to the
blood vessels that transport oxygenated
• In the haemocoel, substance exchange blood to systemic capillaries.
between haemolymph and body cells
occurs through diffusion. • In the systemic capillaries, oxygen
diffuses into the tissues while carbon
• When the heart relaxes, haemolymph dioxide diffuses from the tissue into the
flows back into the heart through tinanyterior capillaries.
openings called ostium.
• The deoxygenated blood is then returned
aorta to the heart atrium through the veins.

anterior • As the blood flows in one direction, the
aorta fish circulatory system is known as a
aorta single circulatory system.

ostium gill capillaries

posterior mixed blood

aorta heart

ostium ostium
haemocoel
heart FIGURE 10.4 The open artery
circulatory system in insects heart
posterior ventricle
Indicator: atrium
FIGURE 10.3 Dorsal view of oxygenated blood
insect heart deoxygenated blood vein
mixed blood
mixed blood
systemic capillaries

FIGURE 10.5 The blood circulatory system of fish

170 10.1.4

CLOSED CIRCULATORY SYSTEM Circulatory System of Humans

Circulatory System of Amphibians • The human heart consists of four
• The heart of an amphibian has three chambers, chambers: two atria and two ventricles
that are separated completely.
that is, two atria and a ventricle. Unlike the single
circulatory system of fish, blood flows in two • Humans have a double circulatory
directions: pulmocutaneous circulation and system. This means that in one
systemic circulation. Therefore, this system is complete circulatory cycle, blood
known as a double circulatory system. flows in the blood vessels through the
• Amphibians are said to have an incomplete double heart twice. As there are two different
circulatory system because the deoxygenated circulations, humans are said to have
blood and the oxygenated blood are mixed. a complete double circulatory
• Pulmocutaneous circulation transports blood to system because the deoxygenated
the lungs and skin, and the exchange of gases blood and the oxygenated blood do
takes place here. Systemic circulation transports not mix.
oxygenated blood to the body tissues and returns
the deoxygenated blood to the right atrium through Pulmonary circulation
the veins.
• Deoxygenated blood is transported
1 Deoxygenated 2 Oxygenated blood through the pulmonary artery to the
blood from body is from lungs and skin lungs for gaseous exchange.
transported to the is transported by
right atrium. the pulmonary vein • Oxygenated blood from the lungs is
to the left atrium. returned to the left atrium and flows
lung capillaries and skin into the left ventricle.
3 Blood from both
atria enters one lung capillaries
ventricle. Although
pulmocutaneous there is some mixing pulmonary artery CHAPTER 10
circulation of oxygenated and
deoxygenated blood
in the ventricle, most vena cava aorta
of the oxygenated
4 blood remains on pulmonary
12 the left side of the vein
ventricle while the
right 3 left deoxygenated blood right left
atrium atrium remains on the right atrium
side of the ventricle. atrium
ventricle right left
ventricle
systemic circulation ventricle

Indicator:
oxygenated
blood

systemic capillaries systemic capillaries deoxygenated
Indicator: blood

oxygenated blood 4 The ventricle Systemic circulation
then pumps the • Blood is pumped from the heart to all
deoxygenated blood blood through the
mixed blood pulmocutaneous (lungs the body tissues through the aorta.
FIGURE 10.6 The blood and skin) and systemic • Then the deoxygenated blood returns
circulatory system of amphibians circulations.
to the right atrium through vena cava.
10.1.4
FIGURE 10.7 The blood circulatory system of humans

171

TABLE 10.1 Similarities and differences between circulatory systems in complex multicellular organisms
Similarities

The circulatory system is found in all multicellular organisms.

The circulatory system consists of a heart to pump blood or haemolymph (in insects).

The circulatory system functions to transport nutrients and wastes.

The heart has valves that ensure blood flows in one direction.

Differences

Organism Insects Fish Amphibians Humans

Types of Open blood Closed blood Closed blood Closed blood
circulatory
system circulatory system circulatory system circulatory system circulatory system

Number of Single (blood Double Double
circulations
flows in the blood (blood flows in (blood flows in

vessel and through the blood vessel the blood vessel

– the heart once and through the and through the

in a complete heart twice in heart twice in

circulation) one complete one complete

circulation) circulation)

Number of The heart is made Two (one atrium Three (two atria Four (two atria and
heart cavities up of many cavity and one ventricle) and one ventricle) two ventricles)
segments
Separation of Incomplete (some Complete
oxygenated –– oxygenated blood (oxygenated blood
blood and is mixed with the does not mix with
deoxygenated deoxygenated deoxygenated
blood blood in the blood in the
ventricle) ventricle)

10.1Formative Practice

1 State two differences between the circulatory 3 The flatworm is a multicellular organism.
systems of fish and humans. However, the flatworm does not require a
specialised transportation system to move
2 Explain why the blood circulatory system of substances in and out of the cell. Explain
amphibians is considered as a closed and why.
incomplete blood circulatory system.
4 Explain why insects need one separate
system (the tracheal system) to transport
oxygen.

172 10.1.4

10.2 Circulatory System of
Humans
Malaysian Innovation
There are three main components in the circulatory system of humans.
A group of researchers • Blood: A type of connective tissue that is made up of blood plasma,
in Malaysia have
produced a device blood cells and platelets. Blood acts as a medium of transportation.
called MyThrob that • Heart: Functions as a muscular pump that circulates blood to the
can be used as a
smart examination whole body.
and monitoring tool • Blood vessels: Consist of arteries, capillaries and veins that
for heart diseases.
The device studies the are connected to the heart, and transport blood to all
original algorithm that the body tissues.
can detect abnormal
heartbeat and is Structure of the heart
suitable to be used for
monitoring at home. Do you know that your heart is as big as your fist? The
heart is located between the lungs in the thorax cavity
and contains four chambers, namely the left atrium, CHAPTER 10
right atrium, left ventricle and right ventricle. The left
chamber is separated from the right chamber by a muscular
wall called septum.
Atrium receives blood that returns to the heart
while the ventricle pumps blood out of the
heart. The ventricle has thicker walls and
contract stronger than the atrium.
The muscular wall of the left ventricle
is much thicker than the muscular wall
of the right ventricle. This is because
the left ventricle has to generate greater
pressure to pump blood out of the
aorta to the whole body while the right
ventricle only has to pump blood to the
lungs.

Coronary arteries 173
transport oxygenated
blood for heart tissues
while coronary veins
transport deoxygenated
blood.

coarrotenrai rkyoarorntearriies

vceonraonkaoryonvaeriins
TABLE 10.8 The circulatory system of humans

10.2.1 10.2.4 10.2.5

Aorta is the main blood artery that transports The pulmonary artery transports
oxygenated blood to the whole body while the vena deoxygenated blood from the heart
cava is the main vein that transports deoxygenated to the lungs while the pulmonary
veins transports oxygenated blood
blood back to the heart. from the lungs to the heart.

The semilunar vena cava vena kava
valves at the base of
the pulmonary artery aorta
and the base of the aorta
aorta ensures that arteri pulmonari
blood which flows pulmonary artery
out of the heart does
not flow back into the vena pulmonari
ventricle when the pulmonary veins
ventricle relaxes. atrium kiri
left atrium
semilunar valves cionrjaopnabriykuvsepinid
bicuspid valve
atrium kanan
right atrium

injap sabit

incjaoprotnriakruysapridtery right ventricle septum The bicuspid
arteri coronari valve (located
bleefttwastereeiupntmumthe
tricuspid valve and the left
ventricle)
The tricuspid valve ensures that
(locvaetnetrdikeblektawnaenen the blood which
right atrium and the right flows into the
ventricle) ensures that left ventricle
blood which flows into the does not flow
right ventricle does not back into the
flow back into the right left atrium. This
atrium. This valve consists valve consists
of three leaflets. left ventricle of two leaflets.

Brainstorm! The septum separates the left part of the heart
What would happen from the right part of the heart and ensures that
to an individual the oxygenated blood does not mix with the
if the bicuspid deoxygenated blood.
valve does not
close completely FIGURE 10.9 Longitudinal section of a human heart
when the ventricle
relaxes? ICT 10.2

174 Video: Animation of
the heart valves
(Accessed on
21 August 2019)

10.2.4 10.2.5

Composition of human blood Biological Lens

The human blood consists of 55% plasma and 45% cell components. Perfluorocarbon (PFC)
Plasma is the medium of transportation in the body. The components emulsions can be
of blood cells consist of red blood cells or erythrocytes, platelets and potentially used as
white blood cells or leucocytes (Photographs 10.1 and 10.2). artificial blood. Studies
have shown that PFC
has the capacity like
blood to transport
oxygen and carbon
dioxide.

erythrocyte

Plasma (forms 55% of the blood platelet
volume) leucocyte

Leucocytes and platelets (less
than 1% of the blood volume)

Erythrocytes (forms 45%
of the blood volume)

PHOTOGRAPH 10.1 Main components of blood PHOTOGRAPH 10.2
Main structural components of
blood CHAPTER 10

TABLE 10.2 Blood plasma components and the main function of each component

Component Main function

Water Blood plasma consists of 90% water. Water is a medium of
transportation and a solvent for respiratory gas, ions, digestive products
and excretory substances.

Plasma proteins • Fibrinogen plays a role in blood clotting.
• Albumin controls blood osmotic pressure.
• Globulin is a type of antibody that is involved in the body’s defence.

Solutes – nutrients such • Nutrients are important for energy, growth and maintenance of health.
as glucose, excretory • Excretory substances are toxic substances that need to be disposed
substances such as
urea and respiratory gas off from the body.
• Oxygen is required in the respiration of cells.
Hormones and enzymes
Hormones control physiological activities in the body. Enzymes are
involved in the metabolic processes of cells.

10.2.2 175

Table 10.3 shows the characteristics and functions of each blood cell type.

TABLE 10.3 Characteristics and functions of blood cell types

Blood cell type Characteristics Functions

Erythrocyte • Has an elastic plasma membrane • Each erythrocyte has a
(red blood cell) • The biconcave disc shape haemoglobin which is the red
pigment that gives blood its red
s2id.e0 viemw enables a large TSA/V for efficient colour.
gaseous exchange
pandangan sisi • It does not have a nucleus at • Haemoglobin contains a heme
the mature stage s7o.5thamt more group. The heme group consists
top view haemoglobin can be loaded of an iron atom which is the
into it binding site for oxygen.
FIGURE 10.10 •p aIntdiasnpgarondautacsed in the bone
Erythrocyte structure marrow of bones such as the • Haemoglobin combines with
Platelet sternum and ribs oxygen to form oxyhaemoglobin
• Can live up to 120 days and is in high oxygen partial pressure
destroyed in the liver or lymph conditions.
through the phagocytosis
process. • Oxyhaemoglobin releases oxygen
in tissues or cells when the partial
pressure of oxygen is low.

• Platelets are produced from • Involved in the blood clotting
fragments or scraps of cell process
cytoplasm that originate from the
bone marrows.

• The life span is less than one
week.

FIGURE 10.11 Platelet polypeptide iron
oxygen
Brainstorm!

The red blood
cell of frogs has
a nucleus and is
larger than the
red blood cell of
humans. What are
the advantages and
disadvantages of
nucleated red blood
cells?

Haemoglobin

176

10.2.2

Blood cell type Characteristics and functions
Leucocyte
(white blood • The shape is irregular and is not fixed
cell) • Contains nucleus
• Does not contain haemoglobin
L Granulocytes • Produced in the bone marrow
• Life span is less than five days
• Leucocyte can diffuse out of the capillary pore and fight pathogens in

tissue fluids. It is divided into two types: granulocytes (contain granules)
and agranulocytes (no granules).
• Granulocytes include neutrophils, eosinophils and basophils.
Agranulocytes include lymphocytes and monocytes.

E Neutrophil Eosinophil Basophil
• The nucleus is made up of • The number of basophils
U • The nucleus is made up of
two to five lobes. two lobes. is lowest in the blood
• Releases enzymes that • It contains heparin that
C • Ingests bacterial cells and
dead cells or tissues from fight inflammation and prevents blood clotting
allergy reaction
O wounds by phagocytosis

C

Y

T

E

S Agranulocyte

Lymphocyte Monocyte CHAPTER 10
• Contains a large nucleus with very little • The biggest leucocyte
• Spherical-shaped nucleus
cytoplasm • Ingests bacteria and dead cells or
• Produces antibodies to destroy bacteria and
tissues by phagocytosis
viruses that enter the body
• Can also produce

antitoxins against toxins
that are produced by
bacteria or viruses

PHOTOGRAPH 10.3 Photomicrograph of leucocytes

10.2.2 177

Human blood vessels

Blood capillary

endothelial cells

endothelium endothelium

smooth smooth muscle
muscle connective
tissue
connective
tissue

Artery Vein

venule

arteriole

FIGURE 10.12 Relationship between artery, blood capillaries and vein

ARTERY BLOOD VEIN
Arteries are blood vessels that transport CAPILLARIES
blood out of the heart. The function of the Capillaries rejoin to
artery is to quickly transport blood at a high Capillaries are form larger blood
pressure to the tissues. blood vessels with vessels called
The blood in the artery is under high thin walls, as thick venules. The venules
pressure because of the pumping action of as one cell. Blood combine to form
the heart. capillaries allow the veins that transport
The aorta is the main artery that leaves exchange of gases to blood back to the
the heart. The artery expands when blood occur between blood heart. Vena cava is
is received from the heart. Therefore, the and cells through the main vein that
artery wall is elastic to stop it from breaking diffusion. Nutrients, carries deoxygenated
due to the high-pressured blood that flows excretory substances blood back to the
through it. and hormones heart. The differences
The branches of an artery become small diffuse through blood between arteries,
vessels known as arterioles when they capillaries. capillaries and veins
reach the body tissues. The arteriole are given in Table 10.4.
continues to branch out and ends at the
capillaries. The group of capillaries is called 10.2.3
capillary network.

178

TABLE 10.4 Differences between arteries, capillaries and veins

Characteristics Artery Capillaries Veins
Wall
Wall is thick, muscular Wall is as thick as one Wall is thin, less muscular
and elastic cell, not muscular and and less elastic
not elastiKcaKpaiplailariri
Arteri Vena
Arteri Vena

elastic wall (as thick as one cell) Vena
fibreArteri
Kapilari
lumen
lumen

Lumen wall lumen wall
Very tiny Large
Valve Small
No Contain valves to maintain
Blood pressure No valve except for one-way flow of blood
The direction of semilunar valve at
blood flow the base of the aorta Low Very low
and at the base of the
pulmonary artery From the artery to the From the whole body
vein to the heart
High

From the heart
to the entire body

lumen (middle space) connective CHAPTER 10
erythrocyte tissues

PHOTOGRAPH 10.4 Scanning electron microscope shows the cross section of an arteriole (4000x magnification)

10.2Formative Practice 3 State two differences between the structures
of erythrocyte and leucocyte.
1 What is the function of the bicuspid valve?
4 Explain why the left ventricle has a thicker
2 Explain why some individuals feel nauseous muscular wall than the right ventricle.
and faint immediately after donating blood?
Why do some blood donors need to take
iron pills?

10.2.3 179

10.3 Mechanism of Heartbeat

How is blood circulated to the whole body? In every contraction, the
heart acts as a pump that pumps blood to the whole body. How is every
heartbeat triggered and sustained?

The heart is made up of cardiac muscles (Photograph 10.5) that intersect
and are connected with one another. This arrangement allows electric
impulses to spread rapidly through the heart and at the same time,
stimulates the cardiac muscle cells to contract simultaneously and
uniformly. Cardiac muscles are myogenic. This means that the heart
contracts and relaxes without receiving any impulse signal from the
nervous system. If the cardiac muscles are stored in a warm oxygenated
solution that contains nutrients, these muscles will contract and relax
rhythmically on their own.

PHOTOGRAPH 10.5 Blood circulation in humans
Cardiac muscle tissue
The produced force that enables blood to circulate in humans is
Our World of Biology generated by the pumping of the heart and the contraction of the
skeletal muscles.
The “Medtronic
Micra” pacemaker left atrium
is the smallest
artificial pacemaker sinoatrial node
in the world. The
size is about the right atrium bundle of His
size of a vitamin atrioventricular node left ventricle
pill and is placed in
the heart without right ventricle
surgery. The artificial
pacemaker sends
small electrical
charges to stimulate
heartbeat.

Purkinje fibres

FIGURE 10.13 The location of sinoatrial node, atrioventricular node,
bundle of His and Purkinje fibres

180 10.3.1

Pumping of the heart The pacemaker generates electrical impulses
that spread rapidly through both walls of
The contraction of the heart is initiated and the atrium and causes the atrium to contract
coordinated by the pacemaker. The pacemaker rhythmically. The main pacemaker is called
is a group of specific heart muscle cells that sinoatrial node (SA). The sequence of heart
initiates the rate of heart contraction and is muscle contraction that causes the pumping is
located at the right atrium wall (Figure 10.14). shown in Figure 10.14.

1 The sinoatrial node (SA) generates 2 Electrical impulses spread rapidly
electrical impulses. in both the atria, causing the atria
to contract simultaneously. The
sinoatrial nodes contraction of the atria helps to pump
(SA nodes) blood into the ventricles.

atria

Purkinje fibres AR ventricles

4 The electrical impulses spread atrioventricular node (AV node) CHAPTER 10
from the apex of the heart to the
whole ventricle wall. As a result, the
ventricles contract to pump blood out
to the lungs and body.

bundle of His Across the fields

apex of Electrical impulses
the heart in the heart can
be detected by
3 Purkinje fibres putting electrodes
The electrical impulses reach the on the skin. The
atrioventricular node. The electrical electrocardiogram
impulses spread through the bundle of is a record of the
His, and the Purkinje fibres up to the electrical activity
apex of the heart. that triggers every
heartbeat.

FIGURE 10.14 The sequence of heart contraction that causes the pumping of the heart

10.3.2 181

During heart pumping, the lub-dub sound can be heard. Do you know
what causes this lub-dub sound?
The lub-dub sound is the closing sound of the heart valves.

1 The first ‘lub’ sound is produced when
the tricuspid valve and the bicuspid valve
close.
2 The second ‘dub’ sound is
tricuspid valve bicuspid valve produced when the semilunar
valves close.

FIGURE 10.15 The lub-dub sound of the heart semilunar
valves

open valve Contraction of skeletal muscles around the veins
veins
muscle The pumping of the heart helps in the distribution and flow
contraction of blood through the arteries, arterioles and blood capillaries.
contricts vein However, the force produced by the pumping of the heart is
insufficient for the blood flow to continue through the veins and
closed valve return to the heart. Besides, the blood is forced to flow against
the force of gravity. The presence valve in the veins ensures that
the blood flows in one direction to the heart.

muscles relax The blood flow in the veins is assisted by:

FIGURE 10.16 Contraction (a) contraction of the smooth muscles found in the venule and
and relaxation of the foot vein walls;
skeletal muscles
(b) contraction of skeletal muscles around the veins. The
contraction of skeletal muscles presses and constricts the
veins, causing the valve to open and allow blood to flow
towards the heart. The valve is then closed to prevent the
blood from flowing back towards the foot (Figure 10.16).

Brainstorm! 10.3Formative Practice

What would happen 1 Name the main heart 4 In what circumstances would
to the valve in the pacemaker. fingers turn pale?
blood vessels of our
legs if we stand or sit 2 What does the term
for too long? myogenic mean?

3 Explain why a person who
stands too long may faint.

182 10.3.2

10.4 Mechanism of Blood
Clotting
The necessity for blood clotting mechanism
STEM Bulletin
What happens when your finger is injured? Blood will flow from the
Scientists have wound until you apply pressure directly on the wound. The pressure
developed a you apply may appear to restrict bleeding temporarily; however, the
nanomagnetic blood flow is actually stopped by the blood clotting process.
particle that Why must the blood clot on the wound? Blood clotting will stop or
contains thrombin. minimise the loss of blood on the injured blood vessel. Blood clotting
This nanoparticle also prevents microorganisms such as bacteria from entering the
is injected into bloodstream through the damaged blood vessel. The blood pressure is
the injured part also maintained because excessive blood loss will lower blood pressure
to trigger blood to a dangerous level. How does blood clotting occur?
clotting and to stop
bleeding. Mechanism of blood clotting

Blood clotting involves a series of chemical reactions that takes place in
the blood when someone is injured to prevent excessive bleeding.

The coagulated platelets, damaged cells and clotting factors CHAPTER 10
in the blood plasma will form an activator (thrombokinase).
Thrombokinase, with the aid of calcium ions and vitamin K, converts
prothrombin to thrombin.

Prothrombin (inactive Thrombin (active plasma
plasma protein) protein that acts as an enzyme).
Thrombin catalyses the conversion
of fibrinogen to fibrin.

Fibrinogen (soluble) Fibrin (insoluble)

TABLE 10.17 Fibrin is a threadlike protein fibre that
Mechanism of blood clotting forms a network on the wound surface to
trap erythrocytes and to close the wound to
prevent blood loss.

10.4.1 10.4.2 183

Our World of Biology Health issues related to blood
clotting
When you sit for
too long, the risk of Under normal conditions, blood does not
thrombosis in legs clot in blood vessels that are not damaged
will increase. Make because of some anticoagulants such as
sure that you move heparin. What happens when the blood
your legs once in a clotting mechanism of an individual does
while. not function?

Activity Zone HAEMOPHILIA

Work in groups • Haemophilia is an example of an illness that
to collect and prevents blood from clotting.
interpret information
about thrombosis, • Haemophilia is a hereditary illness caused by the
embolism and lack of certain clotting factors in the blood.
haemophilia.
Present your • Excessive bleeding due to small wounds or
findings to the bruises can result in death.
class.
THROMBOSIS

• Formation of a blood clot (thrombus).
• Thrombosis happens as a result of:
– damage in blood vessels, or
– sluggish blood flow that causes clotting factors to
accumulate

EMBOLISM

• When a blood clot is transported by blood flow, the blood clot is
called embolus.

• If the embolus gets stuck in a tiny blood vessel, the blood flow will
stop.

10.4Formative Practice

1 At the end of the blood clotting mechanism, 3 Explain the mechanism of blood clotting.
fibrin will be formed to trap erythrocytes.
Explain the meaning of fibrin and its function. 4 Explain why the formation of blood clots in
the blood vessel can cause a heart attack.
2 Describe two health issues related to blood
clotting.

184 10.4.3

10.5 Blood Groups of Humans
ABO blood group
Do you know your blood group? Human blood is classified into A,
B, AB and O groups. Donation and transfusion of blood is based on
the compatibility of the blood group of the donor and the recipient.
cTaBhnliosaoicsdt baggerocaauinupsstBetthheearnetcigipeinenotnhtahsearnetdibbolodoieds in the blood serum that
Blood group A cells of the donor. Blood
antigen A transfruesdiobnloofdrocmella donor to a recipient must take into consideration
the blood group type of the donor and the recipient (Table 10.6). If
anti-B antibody the blood group of both the donor and receiver is not compatible,
anti-t(Ahcoeaanrgteiubdloadtbiyloonao)nd.tigceenllsB of the recipient will experience agglutination
red blood cell

Blood group AB Blood group O
TABLE 10.5 Antigen and antibody in blood groups
antigBelnoAod groupanBtigen B BgBrloonloouoopdardendgtigrboelounAopsndtBicgeelln on red blood cells 
od group A Blooreddgbrloouopd cAell Antibody in the blood
tigen A serum

body annotigaenntibAodies A red blood cell Antigen A Anti-B
d blood cell arnetid-Bblaonotdibcoedlyl antigen B B anti-A antibodyAntigen B Anti-A
anti-A antibody anti-B antibody
AB Antigen A and Antigen B No
Anti-A and Anti-B
O antigen B No

d group AB BloreoddbglorooudpceOll anti-A antibody
TABLE 10.6 Compatibility of blood donor group with the recipient
antigen B BnloooardendgtigrboelounopsdAcBell
od group A antigBenloAod groupanBtigen B BBloloodd group OCan donate blood to Can receive blood from
blood groups
groupred blood cell blood groups
A and O only
tiagnetnibAodies red blood cell nAo antigens A and AB only CHAPTER 10
bcoedlly anti-A antibody B and O only
B B and AB only A, B, AB and O
anti-B antibody
no antibodies AB anti-A antibody AB only

red blood cell antigen B anti-B aOntibody A, B, AB and O O only

d blood cell anti-A antibody

d group AB Blood group O Rhesus Factor
antigen B
red blood cell Another antigen found on the surface of the red blood cells is the
no antigens Rhesus factor (Rh factor). The red blood cells of an individual
with the Rh factor or antigen D are known as Rh-positive. An
antibodies anti-A antibody individual who does not possess the Rh factor or antigen D is known
cell anti-B antibody as Rh-negative.

FIGURE 10.18 Antigens and If the blood of a Rh-positive donor mixes with the blood of a Rh-
antibodies in different blood negative recipient, the blood of the recipient will react by producing
groups the Rhesus antibody or anti-D antibody. When the recipient receives
another dose of Rh-positive blood, the Rhesus antibody will cause the
agglutination of the donor blood cells. This situation could result in
the death of the recipient.

10.5.1 10.5.2 10.5.3 185

Pregnancy and the Rhesus factor

Usually, problems During the last month of However, the Indicator:
will arise when an pregnancy, fragments concentration
Rh-negative mother of foetal blood cells of antibodies Rh-positive
marries an containing antigen D produced is
Rh-positive father cross the placenta not enough Rh-negative
and conceives an and enter the blood to affect the
Rh-positive foetus. circulation of the mother. first child. But Anti-D
the anti-D antibodies
As a result, the white antibodies
blood cells in the will last in The problem arises when
mother’s blood will react the blood the second child is also
and produce anti-D circulatory Rh-positive. The anti-D
antibodies that will system of the antibodies that are present
flow back through the mother. in the mother’s blood cross
placenta into the foetal the placenta and destroy
blood circulatory system. the red blood cells of that
foetus. The symptoms
The antibodies will destroy of this disease are called
the red blood cells of the erythroblastosis fetalis.
Rh-positive baby before The second foetus dies if
or immediately after birth. the blood is not replaced
with Rh-negative blood
10.5Formative Practice through blood transfusion.

In a less serious situation,
the baby may suffer from
anaemia and mental
retardation. However,
this problem can now be
addressed by treating
the affected mother with
anti-Rhesus globulins after
the first pregnancy to stop
the formation of anti-D
antibodies.

1 State the blood group which is the universal The first pair of parents: B and O
donor. The second pair of parents: A and B
The third pair of parents: AB and O
2 Predict what will happen if the blood
group of both recipient and donor is not
compatible. Match the babies with their correct parents.

3 Three babies P, Q and R have blood groups 4 An Rh-positive male marries an Rh-negative
B, O and AB respectively. Three pairs of female. The first Rh-positive child is alive but
parents have the following blood groups: the second child who is also Rh-positive did
not survive. Explain why.

186 10.5.4

10.6 Health Issues Related to the
Human Circulatory System
Activity Zone
The necessity for a healthy circulatory system
Work in groups
and conduct a A healthy circulatory system is important to ensure optimum health.
case study on How do we ensure that our circulatory system is healthy? Among the
the practices of practices for maintaining the circulatory system are a balanced intake of
maintaining a healthy food that is low in fat and regular exercise. The practice of not smoking
human circulatory and not drinking alcoholic drinks also ensures a healthy circulatory
system. system.

Cardiovascular diseases

Do you know that cardiovascular diseases are the leading cause of
death in our country? Cardiovascular diseases include diseases related
to the heart and the blood circulatory system such as atherosclerosis,
arteriosclerosis, angina, hypertension, myocardial infarction (heart
attack) and stroke.

Activity Zone CARDIOVASCULAR DISEASES CHAPTER 10

Discuss a suitable • Atherosclerosis is the formation and deposition of plaque on the
treatment for heart artery walls.
failure.
• The plaque is formed from cholesterol, lipid, dead muscle tissues
and coagulated platelets.

• The plaque will clog and narrow the lumen in blood vessels.

• The restricted blood flow can cause hypertension.
• Hypertension causes fine arteries to break and the patient can suffer

from stroke if this happens in the brain.
• Stroke is also caused by blood clots (thrombus) that clog the flow

of blood in the brain.

• Atherosclerosis is the early stage of arteriosclerosis.
• Arteriosclerosis occurs when calcium is deposited on the plaque

and causes the artery to become hard and lose its elasticity.

• If the lumen of the coronary artery (artery for the heart) is narrowed,
the insufficient oxygen supply to the heart muscles can cause
angina (severe chest pain).

• If the artery is completely clogged, myocardial infarction (heart
attack) will occur.

PHOTOGRAPH 10.6 Myocardial infarction (heart attack)

10.6.1 10.6.2 187

artery

blood clot restricts the flow
of blood

coronary
artery

plaque is
formed in the
artery

dead cardiac
muscle tissues

STEM Bulletin FIGURE 10.19 Formation and deposition of plaque on artery wall

Nanotechnology is What is the treatment for a patient who suffers from heart failure? What
used in the diagnosis are the risk factors that contribute to cardiovascular diseases and what
and treatment of can we do to ensure that the cardiovascular system is healthy?
atherosclerosis and
plaque formation 10.6Formative Practice
in arteries. In this
technique, nanoparticles 1 What is the meaning of 3 In your opinion, what are the
are designed to myocardial infarction? factors that contribute to an
resemble high-density individual’s risk of getting
lipoprotein cholesterol 2 Explain how stroke happens. cardiovascular disease?
(HDL) (“good”
cholesterol) to help 4 Explain how atherosclerosis
reduce plaque. happens.

188 10.6.1 10.6.2

10.7 Human Lymphatic System
The formation of tissue fluid
In addition to the blood circulatory system, there is one more system
in the body whose function is closely related to the blood circulatory
system. This system is called the lymphatic system. The formation of
tissue fluid is illustrated in Figure 10.20.
1 Blood that reaches the arterial end of the 2 This pressure allows the blood
blood capillary has a high pressure due to the plasma to diffuse continuously
small diameter of capillaries and the pumping from the blood capillaries to the

force of the heart. intercellular space.

blood plasma cell

arteriole

oxygenated deoxygenated
blood at a high blood at a low
pressure
pressure

tissue fluid

blood capillary

lymphatic capillary

FIGURE 10.20 Exchange of substances between blood capillaries and body cells CHAPTER 10

3 • Blood plasma that occupies the 4 • Tissue fluid allows the exchange of
intercellular space and constantly • materials in the blood and cells to
• bathes cells is called tissue fluid. • occur.
Nutrients and oxygen diffuse from
The tissue fluid does not contain tissue fluid to body cells.
any erythrocyte, platelet and Simultaneously, excretory products and
plasma protein because these carbon dioxide diffuse from body cells
are too large to diffuse out of the to blood capillaries through the tissue
blood capillaries. fluid.

Lymph formation and components of the lymphatic system

At the venule end of the blood capillary, blood plasma is hypertonic compared to the tissue fluid
surrounding it. Blood pressure is also lower. As a result, the reabsorption of water, mineral salts and
waste takes place in the venule capillary.

However, only 85% of the fluid that leaves the blood at the arteriole end of blood capillary diffuses
back into the venule end. What happens to the remaining 15% that is left in the intercellular space?
This remainder forms about 4 litres of fluid that is lost from capillaries each day. How does the blood
circulatory system regain this fluid?

10.7.1 189

The lost fluid is collected and returned to the blood through the lymphatic capillary, which is the
smallest vessel in the lymphatic system. This fluid is known as lymph and is pale yellow in colour.
Table 10.7 and Table 10.8 show the similarities and differences between lymph with tissue fluid and
blood.

TABLE 10.7 Comparison between lymph and tissue fluid
Similarity

Both contain plasma without the plasma proteins, erythrocytes and platelets.

Differences

Lymph Tissue fluid

Higher content of fat and fat-soluble substances Low content of fat and fat-soluble substances

High content of lymphocytes Low content of lymphocytes

TABLE 10.8 Comparison between lymph and blood
Similarity

Both contain all the contents of plasma such as nutrients, hormones, enzymes, cellular wastes,
respiratory gases and leucocytes.

Differences

Lymph Blood

Does not contain plasma protein, erythrocyte and Contains plasma proteins, erythrocytes and

platelet platelets

The lymphatic capillary wall consists of one layer of cells only. The lymphatic capillary differs from
blood capillary because one of its end is blocked or closed while the other end is connected to the
lymphatic vessel (Figure10.21). Lymphatic capillaries found in intercellular spaces merge to form
a larger lymphatic vessel. Along the lymphatic vessel, there are lymph nodes at certain distances.

lymphatic capillary tissue
cell fluid

arteriole venule lymph
tissue
fluid lymphatic vessel lymphatic
capillary
190 FIGURE 10.21 Lymph formation
valve
10.7.2 10.7.3

The lymphatic system consists of organs such as lymph nodes, spleen, thymus gland, bone marrow,
tonsils and appendix (Figure 10.22). The lymphatic system does not have its own pump to circulate
the lymph along the lymphatic vessel. The flow of lymph is aided by heartbeat pulse, contraction of
skeletal muscles, peristalsis in the digestive tract and changes in pressure during inhalation and
exhalation of breath. In the lymphatic vessel, one-way valves ensure the lymph flows continuously
to the heart. These valves also prevent the lymph from flowing back.

Relationship between the blood circulatory system and the lymphatic system
All lymphatic vessels will eventually join with one of the two main lymphatic vessels which are the
thoracic duct dan right lymphatic duct (Figure 10.22).

The right right lymphatic duct tonsils
lymphatic duct right
receives lymph subclavian thoracic duct
from the right vein left subclavian
hand, chest and vein
right side of the thymus
head and neck. bone marrow
lymphatic
The thoracic vessel spleen
duct receives
lymph from the left
side of the head,
neck and chest,
and all the body
parts below the
ribs.

appendix CHAPTER 10

lymphatic lymph nodes lymph node
capillary lymphocyte
valve 191
10.7.3 blood vessel
tissue fluid

FIGURE 10.22 Lymphatic system

Systemic circulation Pulmonary circulation The thoracic duct will deliver its
lymphatic contents into the left subclavian
right subclavian lymph capillaries vein while the right lymphatic duct
vein node will transport lymph into the right
pulmonary subclavian vein.
right lymphatic capillaries So the lymph collected from the whole
duct body will flow back into the blood
circulatory system. Figure 10.23 shows
lymphatic the relationship between the lymphatic
vessel system and the blood circulatory
system that complement each other.
valve

vein
artery

lymph systemic
node capillaries

lymphatic FIGURE 10.23 Relationship between lymphatic system
capillaries and blood circulatory system

The necessity of the lymphatic system

The necessity of the lymphatic system is summarised in Figure 10.24.

COMPLEMENTS THE NECESSITIES OF BODY DEFENCE
BLOOD CIRCULATORY THE LYMPHATIC
Lymph nodes produce and store
SYSTEM SYSTEM lymphocytes that are involved in the
production of antibodies.
The lymphatic system returns
the excess tissue fluid in the TRANSPORTATION OF FAT-
intercellular space into the SOLUBLE SUBSTANCES
blood flow. The composition,
pressure and volume of blood are Fats and fat-soluble substances
maintained at a normal range. diffuse into the lacteal in the villus
of the small intestine. Lacteals are
FIGURE 10.24 The necessity of the lymphatic capillaries. Lipid droplets
lymphatic system are transported to the thoracic
duct and blood circulatory system
through the left subclavian vein.

10.7Formative Practice 3 State the differences between the composition
of blood plasma, tissue fluid and lymph.
1 Name the two main lymphatic vessels.
4 After eating fatty food, the number of lipid
2 State three main functions of the lymphatic molecules in the lymph increases by 1%.
system. Explain why.

192 10.7.4

10.8 Health Issues Related to the
Human Lymphatic System
Have you ever wondered what would happen if our lymphatic system
Brainstorm! does not function properly? What would happen if the excess tissue fluid
is not returned to the blood flow? Tissue fluid that is not returned to the
Why do our legs blood circulatory system will accumulate in the intercellular space. This
swell after we sit for will result in the swelling of the body tissues. This condition is known
too long? as oedema (Photograph 10.7). Oedema may be caused by a number of
factors (Figure 10.25).

PARASITIC INFECTION

PREGNANCY DEFICIENCY IN • The parasite worm Brugia sp.
The body will produce more PLASMA PROTEIN infects the lymphatic vessel
body fluid to fulfill the needs of a and prevents the flow of
growing foetus. Deficiency of albumin lymphatic fluid.
in the blood.
PROLONGED BEDRIDDEN • The infected part, for example,
PATIENTS leg will swell.

Paralysed or stroke patients with • The patient contracts
limited mobility can suffer from lymphatic filariasis (Photograph
oedema in the legs. 10.8).

• This worm is transmitted
through mosquito bites.

CAUSES OF CHAPTER 10
OEDEMA

normal leg leg with oedema FIGURE 10.25 Causes of
PHOTOGRAPH 10.7 oedema
Oedema
PHOTOGRAPH 10.8
10.8Formative Practice Swollen leg caused by
lymphatic filariasis

1 How do parasitic infections happen? 3 Predict what would happen to the legs of a
patient who has been bedridden for a long
2 Explain what would happen when the tissue period of time? Explain your answer.
fluid fails to return to the blood circulatory
system. 4 Lipid droplets or fat globules cannot diffuse
into the villus blood capillary but must diffuse
through the lacteal. Explain why.

10.8.1 193

Summary

TRANSPORT IN HUMANS AND ANIMALS

Circulatory System Lymphatic System
Components of the
Open Circulatory Closed Circulatory System lymphatic system
System Blood is contained in the • Lymph
Haemolymph closed blood vessel that is • Lymphatic capillaries
flows into the continuous and is distributed • Lymphatic vessel
body cavities to the whole body • Lymph nodes
(haemocoel) and • Lymphatic organs
bathes cells Fish The necessity of the
The fish heart has two Lymphatic System
Insects chambers: an atrium and a • Complements the blood
One or more hearts ventricle circulatory system
pump haemolymph • Transportation of fat-
through the Amphibians soluble substances
haemolymph vessel The heart of an amphibian • Body defence
into the haemocoel consists of three chambers: Health Issues Related to
two atria and one ventricle the Human Lymphatic
System
Humans • Lymphatic filariasis
The human heart consists • Parasitic infection
of four chambers: two atria • Deficiency in plasma
and two ventricles that are protein
completely separated • Pregnancy
• Prolonged bedridden
patients

Circulatory Mechanism Mechanism Blood Groups of Health Issues Related
System of of of Blood Humans to the Human
Humans Heartbeat Clotting Circulatory System
• Blood type A
• Blood Health Issues • Blood type B • Arteriosclerosis
• Heart Related to Blood • Blood type AB • Atherosclerosis
• Blood vessel Clotting • Blood type O • Hypertension
• Rhesus factor • Angina
• Myocardial
• Thrombosis
• Embolism infarction
• Haemophilia • Stroke

194