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Biology
Topic 5: Cell recognition and the immune system
Defence Mechanisms
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Jayden Clauer
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Lymphocyte =
white blood cells
involved in the immune response
Self antigen
= molecule on the
cell surface membrane
of your own body cells
Immunity = means by which the body
protects
itself from
infection
Non-self antigen
= antigen that is not part of the body's own tissue
Pathogen = a
microorganism
that causes
disease
in a host organism.
The two types of defence mechanisms are
specific
and
non-specific
Non specific
responses are
immediate
and are not
specific
to a particular pathogen.
Specific
responses are
slower
and
specific
to each pathogen
Examples of non specific defenses are
physical
/
chemical
barriers and
phagocytosis
Examples of specific responses are
B
and
T
lymphocytes
Examples of barriers are
skin
,
cilia
,
stomach acid
and
tears
Skin
outer layer consists of
flat
,
dead
cells that consist mainly of the protein
keratin
forms a
tough
barrier
Cilia
Tiny hair-like structures lining the
nose
and
gas exchange system
Bathed in
mucus
which is wafted to the back of the
throat
where it can be swallowed
Stomach acid
low
pH
kills pathogens
Tears
contain
lysozymes
which digest the
cell walls
of bacteria