Innate Immunity: Physical barriers

1. Immunity: Part I
Body Defenses Against Infection

2. What is immunity?
• The body’s defense against disease causing
organisms, malfunctioning cells, and
foreign particles Video

3. • Overview of Immunity:
• Reconnaissance, Recognition, and Response
• Two major kinds of defense have evolved that
counter threats:
– Innate immunity
– Adaptive immunity
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

4. Innate Immunity
• Is present before any exposure to pathogens
and is effective from the time of birth
• Involves nonspecific responses to pathogens
• aka. Nonspecific Defenses or Innate Immunity
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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5. Innate Immunity Includes:
• Species resistance
• Physical barriers
• Phagocytic cells
• Immunological surveillance
• Interferons
• Complement system
• Inflammation
• Fever
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

6. Adaptive Defenses
• Also called:
– Specific defenses
– Specific immunity
– Acquired immunity
• Develops only after exposure to inducing
agents such as microbes, toxins, or other
foreign substances (acquired)
• Involves a very specific response to pathogens
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

7. Innate Immunity

8. aka. Mechanical Barriers

9. External Defenses
~Skin~
- The dead, outer
layer of skin, known
as the epidermis,
forms a shield
against invaders and
secretes chemicals
that kill potential
invaders
- You shed between
40 – 50 thousand
skin cells every day!

10. External Defenses: Hair
http://www.hairdirect.com/hair/systems/s
kin/hd10.aspx
http://www.hmh.net/adamhealth/In-
Depth%20Reports/10/000032.htm

11. • Secretions of the skin and mucous membranes
– Provide an environment that is often hostile to
microbes
• Secretions from the skin
– Give the skin a pH between 3 and 5, which is
acidic enough to prevent colonization of many
microbes
– Also include proteins such as lysozyme, an
enzyme that digests the cell walls of many
bacteria
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

12. Sweat
• http://www.examiner.com/article/wiping-your-sweat-away-can-actually-
make-your-workout-harder
Tears
• http://creativephotographymagazine.com/30-heart-touching-photographs-
of-tears/

13. External Defenses
~Mucous and Cilia~
- As you breathe in,
foreign particles and
bacteria bump into
mucus throughout
your respiratory
system and become
stuck

14. External Defenses
~Mucous and Cilia~
- Hair-like structures
called cilia sweep this
mucus into the throat
for coughing or
swallowing

15. External Defenses
~Saliva~
- Saliva contains many
chemicals that break down
bacteria
- Thousands of different types
of bacteria can survive these
chemicals, however

16. External Defenses
~Stomach Acid~
- Swallowed bacteria are
broken down by incredibly
strong acids in the stomach
that break down your food
- The stomach must produce a
coating of special mucus or
this acid would eat through
the stomach!

17. Urinary Tract
• Urine flushes the urinary passageways

18. Reproductive Tract
• Glandular secretions flush structures of the
reproductive system

19. Think of the human body as a
hollow plastic tube…
Substances enter within the hole in the tube,
but it never actually enters into the solid
plastic material directly.
Tube inner surface
~Digestive System~
Plastic interior
~Body~
Tube outer surface
~Skin~

20. Escherichia coli
is common and plentiful in all of our
digestive tracts. Why are we all not
sick?
- These bacteria are
technically outside the
body and aid in digesting
material we cannot
- Only if E.Coli are
introduced in an unnatural
manner can they break
through the first line of
defense and harm us