2Key ConceptsHow does the body’s first line of defense guard against pathogens?What happens during the inflammatory response?How does the immune system respond to pathogens?How does HIV affect the immune system and how does it spread?
4PreviewYou eyes are glued to the video screen. Enemy troops have gotten through an opening in the wall. Your soldiers have held back most of the invaders. However, some enemy soldiers are breaking through the defense lines. You need your backup defenders. They can zap invaders with their more powerful weapons. If you soldiers can fight off the enemy until the backup team arrives you can save your fortress. By eliminating pathogens that can harm you cells, your body maintains homeostasis.
5Barriers that keep Pathogens out Three lines of defenseSkin-pathogens may fall off with dead skin cells. If they stay on the skin they must get through the tightly packed dead cells that form a barrier on top of living skin cellsMost pathogens get through the skin only when it is cut
6(2) Breathing passages Pathogens can enter the body when you inhale The mucus and cilia trap and remove most of the pathogens that enter the respiratory systemYou may also sneeze or cough forcing pathogens out of your body
7(3) Mouth and Stomach Some pathogens are found in foods Saliva in your mouth contains chemicals and your stomach produces acidMost pathogens that you swallow are destroyed by saliva or stomach acid
8The Inflammatory response Second line of defenseFluid and white blood cells leak from blood vessels into nearby tissuesWhite blood cells then fight the pathogensGeneral response-its response is the same regardless of the pathogen
9White blood cells Disease fighters Phagocyte-involved in the inflammatory response, engulfs pathogens and destroys them by breaking them down
10InflammationBlood vessels widen increasing the flow of blood to the areaMore disease fighting white blood cells are delivered to the areaEnlarged blood vessels and the fluid leak out of them and make the affected area red and swollenIt will also feel slightly warmer than normal
11FeverChemicals produced during the inflammatory response cause a fever it helps your body fight the infectionSome pathogens do not grow and reproduce well at higher temperatures
12The immune system Third line of defense Immune response and it is controlled by the immune systemCells of the immune system can distinguish between different kinds of pathogens. Immune system cells react to each kind of pathogen with a defense targeted specifically at that pathogen
13(2)White blood cells that distinguish between different kinds of pathogens are called: lymphocytesThere are two major lymphocytes T cells and B cells
14T CellsIdentify pathogens and distinguish one kind of pathogen from anotherEach kind of T cell recognizes a different kind of pathogenT cells recognize marker molecules called antigens and they are found on each pathogenAntigens are molecules that the immune system recognizes either as part of your body or as coming from outside your body
15B CellsB cells produce proteins that help destroy pathogens these proteins are called antibodiesEach kind of B cell produces one kind of antibody and each kind of antibody has a different structureAntigen and antibody molecules fit together like pieces of a puzzleWhen antibodies bind to the antigens on a pathogen they mark the pathogen for destructionOthers keep pathogens from attaching to the body cells that they might damageOthers make it easier for phagocytes to destroy the pathogens
16AIDS Caused by a virus that attacks the immune system HIV is the only kind of virus known to attack the human immune system directly and destroy T Cells