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Non Specific Responses ­ Primary
Defences
The Skin ­ This is the main primary defence. The outer
layer is called the epidermis which is made up of
layers of cells called Keratinocytes. These cells are
produced at the base of the epidermis and migrate to
the surface of the skin. As they migrate, the cytoplasm
is replaced by the protein Keratin. This process is
called Keratinisation and the layers of dead cells act
as a protective barrier.
Mucus Membranes ­ This protects areas like our lungs,
airways and digestive system. Goblet Cells produce
mucus which traps the pathogens. Then the Cilia
Cells waft this mucus to the back of the throat where it
is swallowed and the pathogens are killed by stomach
acid.…read more

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Non Specific Responses ­
Secondary Defences
· Many pathogens are not trapped by the bodies primary
defence so these must be killed before they cause harm
and/or reproduce.
· This is the phagocytes job.
· There are two types of phagocytes
Neutrophils Macrophages
·Most common type of phagocytes ·Larger cells
·Have a multilobed nucleus ·Manufactured in the bone marrow
·Manufacture in the bone marrow ·Travel in the blood as Monocytes
·Travel in the blood and sometimes ·Tend to settle in the body organs
the tissue fluid especially the lymph node
·Can be found in epithelial tissues ·Have a role in initiating the specific
·Often short-lived response to a disease.
·Released in large numbers…read more

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How do Phagocytes work?
· The phagocytes engulf and destroy the pathogenic cells.
· The pathogens are recognised because they have antigens,
which are chemical molecules on its outer membrane.
· These antigens are specific to the organism.
· Proteins in the blood, called antibodies, attach to the antigens.
· The receptors on the phagocyte bind to the antibodies which are
already attached to the antigen.
· The phagocyte envelopes the pathogen by folding its membrane
inwards.
· The pathogen is then trapped in a vacuole called the
phagosome.
· Lysosomes fuse with the phagosome and release digestive
enzymes called Lysins.
· These digest the bacterium and the harmless end products are
absorbed into the cytoplasm
· This is called Phagocytosis…read more

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Phagocytosis…read more

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Antigens
· These are molecules that stimulates an immune
response
· Antigens are usually large molecules with a specific
shape.
· A foreign antigen is detected by the immune system
and stimulates the production of antibodies.
· These antibodies are specific to the antigen.
· The antigen is often a protein or glycoprotein on the
plasma membrane.
· Our own antigens are recognised by our immune
system and do not initiate a response.…read more

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