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Every day your body is exposed to many
pathogens.
Your body can trap, repel or destroy may of
these intruders.
Most of these pathogens enter the body
through the eyes, nose, mouth and skin.
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Tears-wash away pathogens. They also
contain chemicals that kill some harmful
organisms.
Saliva-destroys may harmful organisms in
your mouth.
Skin-acts as a protective barrier, but
pathogens can enter through cuts, burns, or
scrapes.
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Mucous membranes-tissues lining the
mouth, nose, throat, eyes and other body
openings, trapping the pathogens.
◦ You expel many of the pathogens that your mucous
membranes catch when you sneeze or cough.
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Stomach acid-destroys many pathogens.
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Immune system-a combination of body
defenses made up of cells, tissues and organs
that fight off pathogens.
◦ The immune system snaps into action when a
pathogen breaks through one of the five barriers.
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When pathogens enter the body the immune
system launches an attack.
The inflammatory response occurs if a
foreign invader gets past the five barriers.
This attack occurs in the blood and tissues.
◦ The blood supply to the area increases.
◦ Raises the blood pressure in area causing fluid to
leak from the blood vessels, causing surrounding
tissues to swell. (inflammation)
◦ White blood cells called phagocytes attack the
invaders by surrounding them and eating them.
◦ The phagocytes release special proteins to defend
the body.
 Interferon-is a protein that stops viruses from
reproducing and helps the cells the fight infection.
 If the infection has spread throughout the body a fever
starts which signals the body to produce more white
blood cells, making it difficult for some pathogens to
reproduce.
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What happens when pathogens are able to
survive the inflammatory response?
◦ The body counters with a specific response tailored
to a particular pathogen and the poisons it
produces.
 This not only defends the body from the invading
pathogen, but allows the immune system to remember
the type of pathogen.
 This allows the pathogen to be destroyed more quickly
if the body encounters it again.
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Lymphatic system-a secondary circulatory
system that helps the body fight pathogens
and maintain its fluid balance.
◦ The lymphatic system circulates a watery fluid
known as lymph.
◦ The lymph contain phagocytes called macrophages
that digest and process invading pathogens,
helping the lymphocytes identify them.
◦ Lymphocytes-are special white blood cells found in
the lymph.
 There are three types of lymphocytes, which are
important for fighting off pathogens and disease.
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B cells-formed in bone marrow.
T cells-developed in the thymus gland.
NK cells-natural killer cell, attacks cancerous growths.
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Antigens-substances that send the immune
system into action.
Antibodies-proteins that attach to antigens,
keeping them from harming the body.
Go over 12.4 pg. 339
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Immunity-the body’s ability to resist the
pathogens that cause a particular disease.
◦ You are born with some immunity passed from your
mom.
◦ Your body builds up immunity by being exposed to
pathogens and having certain diseases by
producing memory B and T cells.
◦ Vaccine-a preparation of dead or weakened
pathogens injected into the body to cause the
immune system to produce antibodies.
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Immunization-process or getting vaccinated
because the antibodies your body produces
will build immunity.
◦ Since the pathogens are dead or weakened the
vaccination will not cause you to get sick.
◦ Vaccines have been developed for many diseases
including:
 Polio
 Measles
 Mumps