I
Chapter 3 Immunity and disease
Did you know
Name two diseases caused by a_ bacteria,
Houseflies put their mouthparts onto food
and pump saliva onto it then they suck up
the digested food as a liqud,
b. viruses
2 Give four ways that pathogens can enter the body.
3 Why should people who cook food be careful about their txtrsonal hygiene?
4 Explain why you should always cough and sneeze into a handkerchief,
5 Explain why people sleep under rncisoulto nets in some parts of the world.
Did you know 11,
Some pathogens are able to survive outside the body for quite a while For example, the Covid-19 virus
can survive for several days on hard surfaces such as door handles and light switches.
Defences against diseases the immune system
-
The human body is protected against pathogens by the immune system. The immune system is made
up of three parts innate immune system, adaptive immune system, and passive immune system.
The innate immune system
The innate immune system is the human body's first line of defence. It responds to all pathogens in the
same way—it doesn't distinguish between one type and another. Invading pathogens are dealt with very
quickly and usually within a few hours..
The nose and air passages into the lungs are
lined with cells that produce a sticky mucus. Dirt and bacteria in the air get trapped in this mucus_Tiny
hair-like cilia move the mucus up to the throat where it is swallowed or
expelled out.The skin is a very efficient protective barrier_ However, if it is damaged, the blood forms a
clot, which quickly
mucusixoducingcans
plugs the hole and keeps microorganisms out,
ciliated cell
O X F O R D
1. 1. 411, 101. 11414
-
1■ 11Mmiam - ...:.'
The stomach produces hydrochloric acid is kills any pathogens that might tx.
taken in with food or
The wound es &cocked
 by fibres and red
stomathac'd
its
•
drinks.
-
White cellS
squeeze
through
capillary
wails.
capinarY
(cut open)
Any pathogens that manage to get through these
defences and enter the bloodstream are attacked and
eaten by white blood cells.
1 What is the innate immune system?
2 How long does it take the innate immune
system to deal with pathogens?
0
, . . . . . )
O X F O R D
1 . 0 . 1 . 1 . F . 1 • 1 ,
p , ,
glandinstomach
3 a) What is mucus?
b) Explain how mucus protects the body against
pathogens.
4 What is the body's first line of defence against food
poisoning?
5 Describe what happens to a wound when the skin is
damaged.
6 Describe a way in which enzymes defend the body against
pathogens.
Did you know
•
Tears contain enzymes which are able to
digest pathogens and prevent them from
entering the body around the eyes.
I
Chapter 3 immunity and disease
The adaptive immune system
Unlike the innate immune system, the adaptive immune system remembers which pathogens it has dealt with in the past
and is able to quickly destroy them again. White blood cells produce chemicals called antibodies Each antibody is
specific
This means that an antibody which destroys pneumonia bacteria, for example will not destroy bacteria that cause any
other disease.
Most antibodies work like this:
Each
ryi:e of bacteria Of VifUS has a
differentchemicalonitssurface.similar
to the way all humans have dftietent
hgerptints
When the txxlv detects these
fiats. white bioxl cells
produce antibodies
White cells that produce antibodies can remain in the blood for long periods ready to make more antibodies if the
same pathogen gets into the body again. This protection is called immunity. The more pathogens the body is
exposed to, the more types of antibodies are made and the more diseases the body is immune to.
We are all born with the ability to produce antibodies, but this gradually fades
away as we get older. By the time you are a teenager or young adult, your ability to produce antibodies will have almost
disappeared_ So, adults must rely on defence mechanisms against infectious diseases such as chickenpox, measles,
mumps, and scarlet fever, that they built up during childhood. This helps to explain why children have generally coped better
against Coved-1 9 than adults_
•
What is the diflerence between the innate immune
system and the adaptive immune system?
2 Where are antibodies produced?
3 What is a specific antibody?
4 Describe how antibodies destroy a pathogen.
5 Explain what immunity means.
6 Suggest a reason why young children have
generally coped with Covid-19 than adults.
Antibodies can work in different ways,
Some make pathogens stick
together so white blood cells can
eat more of them
quickly. Other
antibodies. called antitoxins,
neutralize the poisons (toxins)
produced by invading pathogens.
The passive immune system. Some diseases can make you very ill. You could die before your white wood cell can make
enough antibodies to save you, Only
danintotheboh,Protectyo stzainjectedec
kE is
im
m un
ens.
A vaccine consisting of dead or weakened pathogens
is called a vaccination. This results in you getting a mild form of the disease ; Inis mild you probably never even notice it.
However, the vaccine is enough to cause the white blood cells to make antibodies against
live pathogens of the same type should get into your body, you will already be protected against them.
You have probably had quite a few vaccines iniected into your body.This is how you are protected against diseases
such as polio, tetanus, mumps measles, and tuberculosis crB)
Some diseases can be prevented or cured by injecting blood serum from a person who has recovered from the disease.
The serum, which is mainly blood plasma, vviii contain antibodies which will destroy the disease pathogens.
1 What is a vaccine?
2 List three diseases that you have been vaccinated against.
3 A woman going to work in Africa had a vaccination for the
serious disease cholera.
She felt weak and ill for about 12 hours after the vaccination but
then recovered
114.6 1
4 1101MIMMIir.-
a. Suggest why the woman was ill lust after having the
vaccination.
b. Explain why it was important for the woman to have the
vaccination
.
(1 1
4
. . •
X.
4, I F I I F *
. R .,
D
Sometimes a booster
vaccination is given to
naintain a high level of
immunityagainstadisease,.
to avoid catching a disease
choosing to live a healthy lifestyle is the
best way to reduce the chances of catching
a disease. There many simple things
you can do to keep healthy and
food thcrotignly
and eat it whilst it is hot.Keep
foodinafridge or freezer until
Bathe Of shower regularly to
remove sweat and dirt, especially
from hair, feet,
needed_
many simple things you can do to
keep healthy and
avoidillness_
arid under your arms.
 cook food thoroughly
and
eat it whilst it is hot. Keep food in a fridge or a freezer until it is needed,



Bathe or shower regularly to remove sweat and dirt especially from hair,
feet, and under the arms. Make sure clothes are changed and washed
regularly,
Washyourhandsthoroughly before handlino food especially after going
to the toilet. Put a plaster over 3 Cut until it heals.
A hand sanitizer can be used ir; add[tron to washing or when soap and water
aren't available.
Wash your hands
thoroughly before
handling food, especially after
going to the toilet. Put a plaster
or bandage over a out until it
heals over
1 Wearing a lace mask in
enclosed spaces such as on a
bus or a train, or when mixing
with people you do not know,
provides some protection
against air-borne pathogens such
as influenza and Covid-19
viruses.
QXFORD
. . . . .
CA