Immunity: Part IBody Defenses Against Infection

What is immunity?

• The body’s defense against disease causing organisms, malfunctioning cells, and foreign particles Video

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• 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

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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