9781422280300

Allergies and Other Immune System Disorders

your urinary tract. Mucus traps and helps destroy microscopic invaders. Your body produces more mucus when it detects invaders. That’s why you need to wipe your nose so frequently when you have a cold, allergies, or the flu. Army Bases The cells that perform most of the day-to-day work of your immune system are born in the tissue that fills the center of your bones. Here, in the bone marrow, immune cells receive basic training so they can perform specialized jobs. The cells mature into different types, depending on what job they are assigned. Some types of cells get all the training they need in the bone marrow. Others move on to the advanced training center, a small organ in your chest called the thymus. After they’ve received their training, immune cells disperse and travel all around the body via the bloodstream. They leave your blood vessels by squeezing through the walls into the fluid that bathes your cells, called lymph. Lymph is transported around the body via a separate set of vessels called the lymphatic system. Part of the immune system, the lymphatic system filters lymph, cleaning out pathogens and dead cells. The filters are at intersections where lymph vessels meet, in special centers called lymph nodes. If you are sick, your lymph nodes may get swollen. That’s because immune cells gather there, bringing in captured pathogens. Lymph nodes and other filtering organs in the immune system, like the spleen and the tonsils, are mustering points where immune cells can send messages to each other about the enemy. Soldiers in the Army Most of the cells of your immune system are white blood cells. They are able to propel themselves around, like amoebas and other single-celled creatures do. Some white blood cells are in charge of identifying invaders. Others release chemicals. The chemicals might damage invaders, or they might summon

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