2. What is a system?
• A group of tissues (organs) work together
to do a task.
• Ex) digestive system, circulatory system,
immune system…
• Function of the immune system is to
protect body from invasion by pathogens.

3. Overview of Body’s
Defenses
Non-Specific Defenses Specific Defenses
First Line of Defense Second Line of
Defense
Immune Response
Skin and Mucous Inflammatory
Response
Non-Specific
WBC (phagocytes)
Specific (diverse)
Antigens/Antibodies
Lots WBC
Memory

4. Non-Specific Defense
• Similar to “walls of a fort” protect by keeping
pathogens out of body
• Body does NOT distinguish one pathogen from
another
• Your body has several non-specific defenses…
1) External- skin and mucous membranes
(1st
line defense)
2) Internal- Inflammatory response
(2nd
line defense)

5. “Skin”
• Physical barrier
• Chemical barrier-
secretes oil and
sweat (lowers pH
skin), tears (contain
enzyme called
lysozyme), and saliva
• Sheds constantly
(1 million cells per
hour)

6. “Mucous Membranes”
• Skin contains natural
openings (nose, mouth,
trachea, esophagus)
• These areas are lined by
mucous membranes
• Secrete mucus traps
foreign objects
• Areas lined with cilia
• Any pathogens make it
past, may be killed by
stomach acids.

7. “Small Scale
Infections”
• The first line of defense has been broken… second line of defense
is triggered to attack any invaders present
• Inflammatory response
• Body’s attempt to destroy pathogens that enter the body when
the skin is injured
• Triggers series of reactions …
1.) Chemical called histamine is released from white blood
cells called basophils
2) Blood vessels in area of injury swell
3) Tissue at injury site swells
4) Temperature in area of injury rises = redness
5) White blood cells called phagocytes move from the vessels
into the injured tissue eat pathogen and damaged skin cells
6) Platelets clot blood and seal infected area

9. • 1) Alarm Signals
• 2) Swelling
• 3) WBC’s Attack
• 4) Redness
• 5) Increase in temperature
Steps to the Inflammatory Response:

10. • 1) Alarm Signals
• 2) Swelling
• 3) WBC’s Attack
• 4) Redness
• 5) Increase in temperature
Steps to the Inflammatory Response: