The immune system The Fortress Analogy

1st Line of Defense- Skin and mucous (The outer wall) Made up of 3 layers: -Epidermis -Dermis -Hypodermis Includes hair and sweat glands Function: Blocks most microbes from entering the body.

Mucous Membranes & Secretions (Inner Wall) Mucous Membranes- Line all the major entry ways into the body. i.e. esophagus, anus, nose… -Usually are acidic to kill incoming bacteria. Secretions such as saliva and tears contain enzymes which digest the bacteria’s cell wall. Cilia sweep mucous and move pathogens out Helpful bacteria protect you from harmful bacteria Function: Kill any microbes that get past the skin.

2nd Line of Defense- Inflammation White Blood Cells release histamines when they come across enemy antigens. Histamines increase the permeability of capillaries. (Capillaries are tiny blood vessels that run throughout your entire body.) WBC’s are sent throughout the body using capillaries and the war begins. WBC release chemicals that create a fever

Histamines Histamines act like a look out or scout. Sound the alarm. Clear the way for the soldiers (blood vessels) Trigger immediate responses (tears, saliva, goosebumps) Sometimes over-react to allergens causing itchy, watery eyes and nose.

Two road systems Lymphatic system- Blood- Ducts and nodes contain and transport white blood cells. Acts as a collection system for fluids in the body. -Nodes swell when bacteria are present. Blood- White blood cells, lymphocytes, histamines and nutrients are transported through the blood. Gathers fluid and white blood cells from the lymph system.

Terms to know: Antigen-a molecule that elicits an immune response. (Carried by bacteria) Antibody- a protein found in blood plasma that attaches to certain antigens and counter-acts it. Phagocytosis- process of “cell eating”- done by white blood cells.

ARMY- phagocytes White blood cells Phagocytes destroy invading bacteria by engulfing it and digesting it Phago-Eating Cyto-Cell Find cells that have been marked by the B-lymphocytes

The Marines- Specialized Cells B-lymphocytes and T-lymphocytes Every bacteria produces their own identifying antigen (Like a uniform) B-cells- Mark bacteria with an antibody T-cells- Kill infected or damaged cells B and T cells make memory cells Memory cells- help your body remember the infection so your body is prepared the next time you are infected. Function: Destroy invading bacteria and remember how to stop it.

Vaccines Immunity is built up against specific invaders. Vaccines-made of a harmless variant of a disease causing microbe. Lymphocytes create memory cells against the specific bacteria or virus. Can get sick from vaccines if your immune system is weak.

REVIEW 1st Line of Defense _______________ 2nd Line of Defense______________ What causes the body to be aware of invasion?__________________. What kind of cells are general killers? _____________________ What kind of cells are specific in what they target?_________________ What cells help your body to remember the bacteria for the next time?_______________