Fighting Diseases

Causes of Disease Pathogens enter the body and either damage

tissues or produce substances that are toxic to the body

The body recognizes pathogens as foreign invaders due to antigens

Antigens are molecules on the surface of pathogens that the immune system recognizes

The body combats disease through the immune system

The Immune-System Response

The human body has three main lines of defense:

1. External barriers (non-specific)

2. Inflammatory response (non-specific)

3. Specific Immune Response

1st Line of DefenseExternal Barriers

(non-specific) External barriers are non-specific, meaning

they will work to keep out all foreign invaders 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

The stomach also contains strong acid and enzymes that can kill pathogens

2nd Line of Defense:Inflammatory Response

The 2nd line of defense is also non-specific or innate.

This means it will respond the same to any antigen

This is the defense system you were born with!

2nd Line of DefenseInflammatory Response

Inflammatory response occurs when tissues are injured by bacteria, toxins, trauma, heat, or other things.

The damaged cells release chemicals such as histamine. These chemicals cause blood vessels to leak fluid into the tissues, causing swelling which helps isolate the foreign substance from further contact with body tissues.

The chemicals also attract white blood cells called phagocytes that "eat" germs and dead or damaged cells. This process is called phagocytosis.

Inflammatory Response

Inflammatory response symptoms

The affected area becomes red, swollen, and warm.

The inflammatory response may also cause a general fever. The increase in body temperature helps fight off the pathogen!

3rd Line of Defense Specific Immune Response

The cells of the immune system are able to distinguish between different kinds of pathogens. The immune system cells then react to each kind of pathogen with a defense that target specifically at that pathogen.

White blood cells that target specific pathogens are called lymphocytes.

B lymphocytes

(B cell)

B lymphocytes

(B cell)

T lymphocyte(helper T

cell)

T lymphocyte(helper T

cell)antigen

Lymphocytes

There are two major types of Lymphocyte: T-cells: Identify pathogens by their antigens B-cells: produce chemicals called antibodies Antibodies bind to the antigens on a

pathogen, inactivate the pathogen, and mark them for destruction by other immune cells.

Each kind of B-cell produces an antibody that bind to only one kind of antigen

Lymphatic system

The lymphatic system is an extensive drainage network that helps keep bodily fluid levels in balance and defends the body against infections.

Lymph nodes help filter out foreign materials and store lymphocytes (white blood cells)

Active Immunity vs. Passive Immunity

Active immunity

- Occurs naturally when the body itself manufactures antibodies through fighting off a disease

- Occurs artificially when induced by a vaccine.- Provides lasting protection

Passive immunity

- Antibodies are introduced into bloodstream of an individual, given from mother to child during pregnancy and breast-feeding

- Provides only short-term protection

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

Aseptic Techniques

A procedure that is performed under sterile conditions

What examples can you think of? In Hospitals? At home? At school?

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