Keeping Pathogens Out

1. Keeping Pathogens Out • 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.

2. The Five Major Barriers • 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.

3. The Five Major Barriers • 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. • Stomach acid-destroys many pathogens.

4. Keeping Pathogens Out • 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.

5. The Immune System’s Nonspecific Response • 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.

6. The Immune System’s Nonspecific Response • 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.

7. The Immune System’s Specific Response • 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.

8. The Lymphatic System • 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.

9. The Lymphatic System • 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.

10. Antibodies • 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

11. Immunity • 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.

12. Immunity • 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