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Innate Immunity: Physical barriers
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Immunity: Part IBody Defenses Against Infection
What is immunity?
• The body’s defense against disease causing organisms, malfunctioning cells, and foreign particles Video
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• 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
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
3m
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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
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
Innate Immunity
aka. Mechanical Barriers
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!
External Defenses: Hair
http://www.hairdirect.com/hair/systems/
skin/hd10.aspx
http://www.hmh.net/adamhealth/In-Depth%20Reports/10/000032.htm
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• 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
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/
- As you breathe in, foreign particles and bacteria bump into mucus throughout your respiratory system and become stuck
External Defenses~Mucous and Cilia~
External Defenses~Mucous and Cilia~
- Hair-like structures called cilia sweep this mucus into the throat for coughing or swallowing
External Defenses~Saliva~
- Saliva contains many chemicals that break down bacteria
- Thousands of different types of bacteria can survive these chemicals, however
- 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!
External Defenses~Stomach Acid~
Urinary Tract
• Urine flushes the urinary passageways
Reproductive Tract
• Glandular secretions flush structures of the reproductive system
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~
Escherichia coliis 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