Download 11.2 Body`s Lines of Defense

11.2 Body’s Lines of
Defense
Unit D – Human Systems
Learning Outcomes Covered in this
Lesson


List the main cellular and noncellular
components of the human defence system
and describe their role.
Describe technological advances and their
role in human health, specifically,
vaccination.
Magic Doctor Video on learnalberta.ca


List all defense mechanisms that your body
uses to prevent disease that are mentioned
in the video.
Discuss with a class and add all answers to
your list.
First Line of Defense: Physical
barriers


Physical barriers that prevent bacteria and
viruses from entering your body.
Includes your skin, cilia and mucus,
stomach acids, and secretions like tears,
saliva and sweat.
Skin


Covers body and organs, preventing
microbe penetration.
Slightly acidic (pH 3-5) conditions inhibit
growth of microbes.
Cilia and mucus


Mucus traps foreign particles and bacteria.
Cilia are small hairs that move in waves,
sweeping the mucus toward the throat
where they can be removed by coughing
and sneezing.
Stomach acid

Hydrochloric acid in your stomach plays no
role in digestion (breaking down of food),
but kills bacteria that may enter your body
with your food.
Lysozyme


An antimicrobial enzyme that destroys cell
walls of bacteria, ultimately killing them.
Found in tears, saliva, sweat and mucus.
Second Line of Defense: Phagocytosis
and Inflammation


Occurs when an invader has entered your
body, but your body does not know the
identity of the invader.
White blood cells called macrophages start
off this process, using phagocytosis.
Phagocytosis


Macrophages engulf and surround the
invading microbes and then release
enzymes that destroy the bacteria.
Dead bacteria, damaged body cells and
dead white blood cells form a think white
liquid called pus.
Inflammatory Response


Describes the swelling, redness, heat and
pain that accompanies phagocytosis.
Localized immune response that prevents
microbes from spreading to other parts of
the body.
Third Line of Defense: The Immune
Response

Describes the body’s response to a
microbe that has been identified by your
body.
B and T Cells: Working Together



Two types of cells involved in the immune
response.
T cells identify invading microbes by
recognizing antigens (markers) on their
surfaces.
After identifying the antigen, different T
cells pass on information to B cells, which
produce antibodies.
Helper T Cells




Macrophages destroy bacteria, but do not
destroy their antigens.
These antigens are pushed to the cell
membrane of the macrophage.
Macrophages join together with helper Tcells.
Helper T cells memorize the shape of the
microbe’s antigen.

Helper T cells tell pass on information
about antigens and stimulate the
production of antibodies by B cells.
B Cells



Produce antibodies.
Each B cell produces a single type of
antibody.
Plasma are B cells that produce large
amounts of antibodies. (Some plasma cells
produce 2000 antibodies/second).
Killer T Cells

Killer T cells puncture cell membranes of
foreign microbes and virus-infected cells,
killing them.
Memory T Cells


“Remember” the shape of the antigen in
case the body is invaded again.
Ensures rapid production of antibodies
upon a second infection.
Suppressor T Cells


Shut down the immune response after
foreign microbes have been destroyed.
If immune response is not shut down,
immune cells will keep attacking body cells,
which can negatively affect normally
functioning organs or tissues.
Student Tasks for Lesson


Complete “Immune Response” questions.
Create a flow-chart outlining the body’s
immune response (to be handed in).