Download L3 Defence Against Disease

L3: Defence Against Disease
Learning Objectives:
1. Describe the body’s first line of defence against pathogens.
2. Explain how white blood cells deal with pathogens in different
ways.
3. Evaluate the effectiveness of vaccinations in preventing disease.
Chemicals in tears kill bacteria.
The skin is the very first
barrier to entry. Sweat
also contains chemicals to
kill bacteria.
Cells in the respiratory tract
produce mucus. Pathogens get
stuck to the mucus. Cilia (tiny
hairs) sweep the mucus into
the stomach.
The First Line of Defence:
Preventing Pathogens Getting In
Blood clots and forms
scabs. This prevents
pathogens getting in.
Hydrochloric acid in
the stomach kills
bacteria.
Second Line of Defence: The Immune System
• White blood cells are a vital part of the immune system as they deal
with pathogens that do enter the body.
• They do this in three main ways:
1. Ingesting – they “eat” and digest pathogens
2. Producing Antibodies – these tag and disable pathogens
3. Producing Antitoxins – these counteract the toxins produced by
pathogens
White Blood Cells Ingest Pathogens
Antibodies
1. White blood cells produce
antibodies that recognise a
site on the surface of the
pathogen called an antigen.
2. Antibodies tag and disable
pathogens by making them
stick together.
3. Other white blood cells
recognise the antibodies
and ingest the pathogens.
1.
2.
3.
Produce Antitoxins
Immunisations (Vaccinations)
• A vaccine containing dead or
inactivated pathogen is
injected into your body.
• Your body will then make
antibodies and memory cells
recognising the pathogen that
stay in your body.
Immunisations (Vaccinations)
• You are now immune to the
disease caused by that pathogen.
• This means that if the pathogen
enters your body, your immune
system will recognise it right away,
make antibodies very quickly, and
get rid of it before you get sick.