Chapter 19, Section 2 The Body’s Defenses Tuesday, April 27, 2010 Pages

Objectives Identify the body’s barriers against pathogens. Describe the role of the inflammatory response in fighting disease. State how the immune system responds to pathogens. Describe HIV and list the ways it can be spread.

Vocabulary Words Inflammatory response Phagocyte Immune response Lymphocyte T cell Antigen B cell Antibody AIDS

Your Body’s Defenses Your body has three lines of defense against pathogens. –The skin –The Breathing passages –The mouth and stomach

The Skin as a Barrier Your skin is the first line of protection. –There are destructive chemicals in the oils and sweat. –Pathogens may come off when dead skin cells are shed. –Keeping your hands clean with soap and water decreases the number of pathogens on the skin.

Skin as a Barrier -- cont’d Pathogens enter your body only when there is a cut or exposure.

Breathing Passages Pathogens are inhaled as you breathe in. The nose, pharynx, trachea, and bronchi all contain mucus and cilia that will trap and remove most of the pathogens that enter the respiratory system. Coughing and sneezing are actions that force the pathogens out of your body.

The Mouth and Stomach Pathogens that are found in food are not mixed with blood or other parts of your body. Your saliva contains chemicals that destroy many of these pathogens. Stomach acids also destroy pathogens.

General Defenses Even with the first line of defenses, pathogens do end up in our bodies. –Cells are damaged. –Inflammatory response is triggered.

Inflammatory Response This is a second line of defense. In the inflammatory response, fluid and certain types of WBC will leak from the blood vessels into the nearby tissues to fight these pathogens. WBC are all disease fighters but there are different types with specific functions.

General Defenses -- cont’d The type of WBC in inflammatory responses are called phagocyte. Phagocytes engulf the pathogens and breaks them down.

The Immune System Immune response is your third line of defense. It is controlled by your body’s Immune System. The immune system cells react to each kind of pathogen with a defense specifically targeted at that pathogen.

The Immune System -- cont’d The WBC that are pathogen specific are called lymphocytes. There are two major types: –T lymphocytes (T cells) –B lymphocytes (B cells)

T Lymphocytes (T Cells) Its function is to identify pathogens and distinguish one from another. T Cells look for marker molecules called antigens. Antigens tells T Cells if it’s supposed to be in your body or not.

B Lymphocytes (B Cells) B Cells produce chemicals (antibodies) that help destroy each kind of pathogens. Each kind of B Cells only produce one kind of antibody.

B Cells -- cont’d Since B Cells produce one kind of antibody, it can only match up with only one type of antigen. It fits together like a puzzle piece.

Acquired Immunodeficiency Syndrome Also called AIDS. A disease caused by a virus that attacks the immune system. –This virus is called human immunodeficiency virus or HIV.

How HIV Infects HIV attacks the immune system directly. HIV enters the T Cells and reproduces inside them and eventually destroys them. Once the T Cells are destroyed, the body loses its ability to fight disease. Most people with HIV will eventually develop AIDS.

How HIV is Spread HIV can only reproduce inside T Cells. HIV can survive outside the body for a short period of time. –Blood, bodily fluids. HIV spreads from one person to another only if body fluids from an infected person come in contact with an uninfected person. –Sexual contact, sharing needles, in utero, transfusion are examples.

Review Questions Name four barriers that prevent pathogens from getting into the body. Explain how each barrier prevents infection. What is the function of the immune system? What is the first line of defense?

Review Questions -- cont’d What is the second line of defense? What is the third line of defense? How is HIV different from other virus pathogens?

Homework Workbook 19.2 (4/28) Extra Credit (4/30)

Extra Credit Choose one only: 1.What is malaria and how is it contracted? What was the relationship between malaria and the Panama Canal? 2.What lifestyle changes must a person who is infected with HIV make? What current therapies are available? How many people in the US and worldwide are infected?