Chapter 18
Communicable
Diseases
Lesson 2
The Body’s Defenses
Against Infection
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 immune
system
A combination of body defenses made up of the
cells, tissues, and organs that fight off
pathogens and disease
 immunity
Your body’s ability to resist the germs that cause
a particular disease
 inflammation
The body’s response to injury or disease, resulting
in a condition of swelling, pain, heat, and redness
 lymphatic
system
A secondary circulatory system that helps the body
fight pathogens and maintain its fluid balance
 lymphocytes
The white blood cells in the lymphatic system
 antigen
Any substance released by invading pathogens
 antibodies
Proteins that attach to antigens, keeping them from
harming the body
 vaccine
A preparation of dead or weakened pathogens that
causes the immune system to produce antibodies
In this lesson, you will learn to
 name the body’s first line of defense against pathogens.
 describe how the immune system functions.
 explain how antibodies protect the body.
 practice behaviors that keep your immune system healthy.
Sequencing
Draw a concept map that
shows different ways your
body works to defend itself
from pathogens entering
your body. Use Figure 18.2
as a guide.
Body’s
Defenses
Your Body Defends Itself
The Five Major Barriers
Tears
Saliva
Mucous
Membranes
Skin
Stomach
Acid
Your Body Defends Itself
If a pathogen gets past one of the five major
barriers, your body’s immune system takes over.
immune system A combination of body defenses made up of
the cells, tissues, and organs that fight off
pathogens and disease
Your Body Defends Itself
Your immune system’s two main responses are the
nonspecific response and the specific response.
Together, these responses provide immunity.
immunity Your body’s ability to resist germs that
cause a particular disease
Nonspecific Immune Response
The nonspecific response begins with inflammation.
inflammation The body’s response to injury or disease, resulting in
a condition of swelling, pain, heat, and redness
With inflammation, the body starts producing a
protein called interferon to stimulate the body’s
immune system.
Specific Immune Response
Each specific response is customized to attach a
particular pathogen and its toxins.
Our immune system can “recognize” pathogens it
has already battled.
The Lymphatic System
The fluid circulation in the lymphatic system is
called lymph (LIMF).
lymphatic system A secondary circulatory system that helps
the body fight pathogens and maintains its
fluid balance
The Lymphatic System
The two types of lymphocytes are B cells and T
cells.
lymphocytes The white blood cells in the lymphatic system
B cells form in the bone marrow. T cells develop in
the thymus gland.
The Lymphatic System
Macrophages are found in the lymph.
Their purpose is to attach themselves to invading
pathogens and destroy them.
Antibodies and Antigens
Lymphocytes react to antigens.
antigen Any substance released by invading pathogens
The immune system responds to antigens by
producing antibodies.
antibodies Proteins that attach to antigens, keeping them
from harming the body
Antibodies and Antigens
B cells produce a specific antibody for each
specific antigen.
T cells either stimulate the production of B cells or
attack pathogens directly.
The two types of T cells are helper cells and killer
cells.
Immunity
Everyone is born with a natural immunity.
Immunity also develops when a vaccine is used.
vaccine A preparation of dead or weakened pathogens that
causes the immune system to provide antibodies
Immunity
To keep your body healthy, it is
important to keep vaccinations
current.
Vaccines protect not only you but
those around you.
Lesson 2 Review
What I Learned
Vocabulary Define the term antigen. Name two types
of white blood cells your immune system produces to
fight antigens.
Lesson 2 Review
What I Learned
Recall What is the lymphatic system? How does it
protect your body against disease?
Lesson 2 Review
What I Learned
Explain What is the body’s first line of defense against
pathogens?
Lesson 2 Review
Thinking Critically
Analyze How does a fever help fight an infection?
Lesson 2 Review
Thinking Critically
Evaluate How do vaccines help protect the health of
the community?
End of
Chapter 18
Communicable
Diseases
Lesson 2
The Body’s Defenses
Against Infection
Click for:
>> Main Menu
>> Chapter 18 Assessment