KEY CONCEPT The immune system consists of organs, cells, and molecules that fight infections.

The immune system is the body system that fights off infection and pathogens.

Think of your body as a heavily guarded castle Think of your body as a heavily guarded castle. When pathogens invade they must break down the outer wall or find a way around it. If the intruders get past the physical barriers, they must face your body’s fighters in hand-to-hand combat. Invaders are winning= you are sick Your body is winning= you are healthy

What is our first line of defense? SKIN!!!!!!! Cuts and wounds are entry points What are the other entry points? Eyes Nose Ears Mouth Excretory Organs (lungs)

Skin is a physical barrier to infection It is your first line of defense! Mucous membranes in these openings trap pathogens entering the body. The circulatory system transports immune cells.

SKIN First line of defense against pathogens Protection from infection Oil glands in skin Inhibit the growth of bacteria

Cut yourself Bleed Form blood clot Blood clot dries out- Scab is formed Skin cells divide and multiply- (mitosis) Scab falls off

Six main types of white blood cells phagocyte- Destroys viruses, bacterium, and fungi by engulfing them Ex: macrophage

2) T cells- Destroy body cells that are infected 3) B cells- Produce proteins that inactivate pathogens that haven't infected body cells yet

4) Complement Proteins: made by white blood cells, and weaken pathogen’s cell membrane allowing water in so it will burst

5) Antibodies: made by B cells Attack pathogens by “binding” themselves to the pathogen to prevent them from attacking healthy cells Cause pathogen’s to clump, making it easier for phagocytes to engulf and destroy

6) Interferons: produced by body cells infected by a virus Stimulate uninfected body cells to produce enzymes that will prevent viruses from entering and infecting them ***If a virus can’t enter it- it can’t reproduce!