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Causes of Disease
many diseases are caused by microorganisms, called pathogens
they enter the body (called an antigen) and either damage tissues or produce substances that toxic to the body
the body combats disease through the immune system
The Immune-System Response
the human body have many defenses against infection
They are categorized into THREE lines of defense:1. External (integumentary system)
2. Non-specific (Innate) Immunity
3. Specific Immunity
1st Line of DefenseIntegumentary System
the first line of defense is an external or physical barrier
the human skin, if unbroken, forms an almost impenetrable barrier against microorganisms
cells in the nasal passages and pharynx secrete sticky mucus that traps microorganisms and digestive enzymes in the mucus can destroy most microorganisms
2nd Line of Defense Non-specific (Innate) Immunity
if invaders get pass the 1st line of defense and enters the body, the 2nd line of defense, a complex network of organs, works to get rid of the infection
Lymphatic system
2nd Line of DefenseThe Lymphatic System
white blood cells (called leukocytes) seek out and destroy invaders and are produced in the lymph nodes
Three types of defending leukocytes:
Macrophages (“big eaters”, pus) – engulf antigens Neutrophils - engulf antigens Natural killer (NK) cells – kill invaded cells
Inflammatory Response
Histamine release – increases blood flow
Increase capillary permeability: Edema – swelling, pressure on nerves = pain Immune cells circulate better
Elevated temperature – fever, helps with attack against pathogens
3rd Line of Defense Specific Immunity
Lymphocytes (another class of leukocytes) can recognize antigens and direct an immune response
B lymphocytes
(B cell)
B lymphocytes
(B cell)
T lymphocyte(helper T
cell)
T lymphocyte(helper T
cell)
antigen
3rd Line of Defense Specific Immunity
B cells – produce and display antibodies (Plasma B cells), and some also become memory B cells
antibodies are protein molecules that protect the body from invaders by attaching to the surface of the invader which makes it more easily identifiable to macrophages
antibodies are unique to each antigen form a response against antigens, the surface of an invader may have many different antigens
Helper T cells: release cytokines that activate more B
cells, Killer T cells, and macrophages Kill viruses with toxins
After the infections is over:
- B cells and T cells die, except for memory B cells
T-Killer cells a.k.a. cytotoxic T cells
Match the template with the viral antigen and kill the virus with toxins; also kill cancer cells
Active Immunity
lasting protection against pathogens through the production of antibodies
can be acquired naturally, when a person recovers from an invaders and has produced antibodies against it OR
artificially, by the injection of vaccines made of dead or weaken invaders, or even isolated antigens, the body will produce antibodies to provide immunity towards the pathogen
Prevention of Disease Summary Proper sterilization and/or cleaning of instruments
& surfaces disinfectants (chemical that kill microorganisms on
surfaces) E.g., bleach
Proper use of antiseptics (chemicals that can be used on the skin) e.g. mouthwash, antibacterial soap
Proper use of antibacterial medication Vaccinations (dead form of pathogen) Natural human immune response
Let’s see this all in action
http://highered.mcgraw-hill.com/classware/ala.do?isbn=0072965819&alaid=ala_1032810&showSelfStudyTree=true
The Immune Response
Why is it necessary to have so many different types of cells in the immune system?
http://www.youtube.com/watch?v=IWMJIMzsEMg