Download The Body`s Lines of Defense

The Immune System
The Body’s Lines of Defense
Disease
 Disease is defined as a condition that impairs or
interferes with the well being of an organism.
 Some diseases are caused by the breakdown of
normal body processes while others result from
pathogenic agents.
 Pathogenic organisms are disease-producing
organisms, which can be viruses, bacteria, protists, or
fungi.
Purpose of the Immune
System
 The immune system protects the body from infection
and invasion by foreign substances.
 It also recognizes and destroys altered cells.
http://www.youtube.com/watch?v=CeVtPDjJBPU
Three Lines of Defense
 The human body must constantly defend itself against
the many unwelcome intruders it encounters in the air,
in food and in water.
 It must also deal with abnormal body cells that
sometimes turn into cancer.
 Three lines of defense have evolved to help resist
infection and possible death from fatal illnesses.
Three Lines of Defense
(cont’d)
 The first two lines of defense are considered
nonspecific immune responses, meaning they do not
distinguish one microbe from another.
 The third line of defense is a specific immune response
that reacts in specialized ways to various intruders.
OVERVIEW- RECAP
 What is the purpose of the immune system?
 What is disease?
 How many lines of defence does the body have?
 Why would this be important?
 What does non-specific immune response mean? What
does specific?
 Why would there be both?
The First Line of Defense
 The body’s first line of defense against foreign invaders
is largely physical…The skin and mucus membranes
form a barrier against viral and bacterial invaders.
 Like a medieval city that used walls and moats to
defend against attack from outsiders.
The First Line of Defense
(cont’d)
 The skin also has chemical defenses in the form of
acidic secretions, which keep it at a pH range of 3-5,
which inhibits the growth of microbes.
 Lysozyme is an antimicrobial enzyme secreted in
human tears, saliva, mucus secretions and
perspiration. It destroys the cell walls of bacteria, killing
them.
Skin Video
The First Line of Defense
(cont’d)
 In the respiratory passage, invading microbes and
debris become trapped in a layer of mucus or filtered
by cilia.
 In the stomach, there are acids and protein-digesting
enzymes that destroy most of the invading microbes
carried into the body with food.
FIRST LINE- RECAP
 What is the “first line” of defence?
 How does the skin protect the body from attack?
 How do the openings in the skin (mouth, eyes, nose,
etc) make the body vulnerable? What methods have
been developed to protect the body from attack?
The Second Line of Defense
 A second line of defense can be mobilized if the
invader takes up residence in the body.
 This is a nonspecific defense mechanism that relies
mainly on the process of phagocytosis (ingestion of
invading microbes by certain types of white blood
cells).
The Second Line of Defense
(cont’d)
 Leukocytes, or white blood cells, are cells that can
engulf invading microbes or produce antibodies.
 The shape and size of the nucleus, along with granules
in the cytoplasm, can be used to identify different
classes of leukocytes.
The Second Line of Defense
(cont’d)
 When a foreign particles penetrates the skin through an
injury, special white blood cells, known as monocytes,
migrate from the blood into the tissues, where they
develop into macrophages.
 Macrophages = “Big eaters”
 Microbes are engulfed by the macrophage and
destroyed by enzymes within the macrophage.
The Second Line of Defense
(cont’d)
 Another phagocytic response involves white blood cells
known as neutrophils.
 Neutrophils are attracted to chemical signals given off
by cells that are damaged by microbes.
 Neutrophils engulf microbes and release lysosomal
enzymes that digest both the microbe and the white
blood cell.
 The remaining fragments of protein, dead white blood
cell and digested invader are called pus.
The Second Line of Defense
(cont’d)
 Tissue damage due to physical injury also initiates a
localized inflammatory response.
 Inflammatory response = A nonspecific immune response
resulting in swelling, redness, heat and pain.
 So, pus and inflammation are signs that the second line
of defense has been at work.
Inflammatory response
 https://www.youtube.com/watch?v=K3JS_eekIs8
The Second Line of Defense
(cont’d)
 A fever is another example of the body’s system-wide
response to infection.
 When infectious organisms spread throughout your body,
neutrophils and macrophages digest the invaders and
release chemicals into your bloodstream.
 When the chemicals reach the part of your brain that
controls temperature, it raises the temperature.
 The higher temperature makes it harder for a bacteria to
survive.
SECOND LINE- RECAP
 What is the “second line” of defence?
 How do the leucocytes protect the body from attack?
 How does inflammation protect the body?
 Why is it important to have cells from the circulatory
system arrive at the site of infection?
 What is the impact of increased body temp?
 What is an allergic reaction?
Review
 First Line of Defense
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Skin
Mucus
Tears
Saliva
Stomach acid
 Second Line of Defense
 Macrophages
 Neutrophils
 Inflammatory response
Third Line of Defense
 The body’s third line of defense is a specific response
to infection.
 This is known as the immune response and will be
covered tomorrow.
 Immune response
http://www.youtube.com/watch?v=WJEc2GDEfz8
 Magic School Bus
 http://www.youtube.com/watch?v=RFk02G6Q9GU
 Bill Nye http://www.youtube.com/watch?v=GQFUziWNj2c
 Intro video overview
http://www.youtube.com/watch?v=Non4MkYQpYA
Chloe and Nerb… contains info on the anatomy
https://www.youtube.com/watch?v=24IYt5Z3eC4