Transcript Chapter 19, Section 2 The Body’s Defenses

Chapter 19, Section 2
The Body’s Defenses
Tuesday, April 27, 2010
Pages 596 -- 604
Objectives
• Identify the body’s barriers against
pathogens.
• Describe the role of the inflammatory
response in fighting disease.
• State how the immune system responds
to pathogens.
• Describe HIV and list the ways it can be
spread.
Vocabulary Words
• Inflammatory
response
• Phagocyte
• Immune response
• Lymphocyte
•
•
•
•
•
T cell
Antigen
B cell
Antibody
AIDS
Your Body’s Defenses
• Your body has three lines of defense
against pathogens.
– The skin
– The Breathing passages
– The mouth and stomach
The Skin as a Barrier
• Your skin is the first line of protection.
– There are destructive chemicals in the oils
and sweat.
– Pathogens may come off when dead skin
cells are shed.
– Keeping your hands clean with soap and
water decreases the number of pathogens
on the skin.
Skin as a Barrier -- cont’d
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• Pathogens
enter your
body only
when there is
a cut or
exposure.
Breathing Passages
• Pathogens are inhaled as you breathe in.
• The nose, pharynx, trachea, and bronchi all
contain mucus and cilia that will trap and
remove most of the pathogens that enter the
respiratory system.
• Coughing and sneezing are actions that force
the pathogens out of your body.
The Mouth and Stomach
• Pathogens that are found in food are
not mixed with blood or other parts of
your body.
• Your saliva contains chemicals that
destroy many of these pathogens.
• Stomach acids also destroy pathogens.
General Defenses
• Even with the first line of defenses,
pathogens do end up in our bodies.
– Cells are damaged.
– Inflammatory response is triggered.
Inflammatory Response
• This is a second line of defense.
• In the inflammatory response, fluid and
certain types of WBC will leak from the
blood vessels into the nearby tissues to
fight these pathogens.
• WBC are all disease fighters but there
are different types with specific
functions.
General Defenses -- cont’d
• The type of WBC in
inflammatory
responses are
called phagocyte.
• Phagocytes engulf
the pathogens and
breaks them down.
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The Immune System
• Immune response is your third line of
defense.
• It is controlled by your body’s Immune
System.
• The immune system cells react to each
kind of pathogen with a defense
specifically targeted at that pathogen.
The Immune System -- cont’d
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• The WBC that are
pathogen specific
are called
lymphocytes.
• There are two major
types:
– T lymphocytes (T
cells)
– B lymphocytes (B
cells)
T Lymphocytes (T Cells)
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• Its function is to identify
pathogens and
distinguish one from
another.
• T Cells look for marker
molecules called
antigens.
• Antigens tells T Cells if
it’s supposed to be in
your body or not.
B Lymphocytes (B Cells)
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• B Cells produce
chemicals
(antibodies) that
help destroy each
kind of pathogens.
• Each kind of B Cells
only produce one
kind of antibody.
B Cells -- cont’d
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• Since B Cells
produce one kind of
antibody, it can only
match up with only
one type of antigen.
• It fits together like a
puzzle piece.
Acquired Immunodeficiency
Syndrome
• Also called AIDS.
• A disease caused by a virus that attacks
the immune system.
– This virus is called human
immunodeficiency virus or HIV.
How HIV Infects
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• HIV attacks the immune
system directly.
• HIV enters the T Cells
and reproduces inside
them and eventually
destroys them.
• Once the T Cells are
destroyed, the body
loses its ability to fight
disease.
• Most people with HIV
will eventually develop
AIDS.
How HIV is Spread
• HIV can only reproduce inside T Cells.
• HIV can survive outside the body for a short
period of time.
– Blood, bodily fluids.
• HIV spreads from one person to another only
if body fluids from an infected person come in
contact with an uninfected person.
– Sexual contact, sharing needles, in utero,
transfusion are examples.
Review Questions
• Name four barriers that prevent
pathogens from getting into the body.
• Explain how each barrier prevents
infection.
• What is the function of the immune
system?
• What is the first line of defense?
Review Questions -- cont’d
• What is the second line of defense?
• What is the third line of defense?
• How is HIV different from other virus
pathogens?
Homework
• Workbook 19.2 (4/28)
• Extra Credit (4/30)
Extra Credit
Choose one only:
1. What is malaria and how is it contracted?
What was the relationship between malaria
and the Panama Canal?
2. What lifestyle changes must a person who
is infected with HIV make? What current
therapies are available? How many people
in the US and worldwide are infected?