Keeping Pathogens Out

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Every day your body is exposed to many pathogens. Your body can trap, repel or destroy may of these intruders. Most of these pathogens enter the body through the eyes, nose, mouth and skin.

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Tears-wash away pathogens. They also contain chemicals that kill some harmful organisms. Saliva-destroys may harmful organisms in your mouth. Skin-acts as a protective barrier, but pathogens can enter through cuts, burns, or scrapes.

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Mucous membranes-tissues lining the mouth, nose, throat, eyes and other body openings, trapping the pathogens. ◦ You expel many of the pathogens that your mucous membranes catch when you sneeze or cough.

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Stomach acid-destroys many pathogens.

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Immune system-a combination of body defenses made up of cells, tissues and organs that fight off pathogens. ◦ The immune system snaps into action when a pathogen breaks through one of the five barriers.

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When pathogens enter the body the immune system launches an attack. The inflammatory response occurs if a foreign invader gets past the five barriers. This attack occurs in the blood and tissues. ◦ The blood supply to the area increases. ◦ Raises the blood pressure in area causing fluid to leak from the blood vessels, causing surrounding tissues to swell. (inflammation) ◦ White blood cells called phagocytes attack the invaders by surrounding them and eating them.

◦ The phagocytes release special proteins to defend the body.  Interferon-is a protein that stops viruses from reproducing and helps the cells the fight infection.  If the infection has spread throughout the body a fever starts which signals the body to produce more white blood cells, making it difficult for some pathogens to reproduce.

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What happens when pathogens are able to survive the inflammatory response? ◦ The body counters with a specific response tailored to a particular pathogen and the poisons it produces.  This not only defends the body from the invading pathogen, but allows the immune system to remember the type of pathogen.  This allows the pathogen to be destroyed more quickly if the body encounters it again.

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Lymphatic system-a secondary circulatory system that helps the body fight pathogens and maintain its fluid balance. ◦ The lymphatic system circulates a watery fluid known as lymph. ◦ The lymph contain phagocytes called macrophages that digest and process invading pathogens, helping the lymphocytes identify them. ◦ Lymphocytes-are special white blood cells found in the lymph.

 There are three types of lymphocytes, which are important for fighting off pathogens and disease.   

B cells-formed in bone marrow. T cells-developed in the thymus gland. NK cells-natural killer cell, attacks cancerous growths.

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Antigens-substances that send the immune system into action. Antibodies-proteins that attach to antigens, keeping them from harming the body. Go over 12.4 pg. 339

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Immunity-the body’s ability to resist the pathogens that cause a particular disease. ◦ You are born with some immunity passed from your mom. ◦ Your body builds up immunity by being exposed to pathogens and having certain diseases by producing memory B and T cells. ◦ Vaccine-a preparation of dead or weakened pathogens injected into the body to cause the immune system to produce antibodies.

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Immunization-process or getting vaccinated because the antibodies your body produces will build immunity. ◦ Since the pathogens are dead or weakened the vaccination will not cause you to get sick. ◦ Vaccines have been developed for many diseases including:  Polio  Measles  Mumps