The immune system protects the body from invading pathogens with the help of specialized cells called white blood cells. There are many different types of white blood cells, and each plays a specific role to protect against invaders. White blood cells, antibodies, skin, tonsils, mucous membranes, the complement system, the lymphatic system, the spleen, the bone marrow, and the thymus are all part of the immune system, and each part has a specialized function. When a pathogen attacks the body, certain white blood cells create antibodies to kill the pathogen, and other white blood cells attack the pathogen. There are 3 types of immunity within the immune system: innate immunity, active immunity, and passive immunity. Innate immunity is built-in protection you are born with, active immunity is developed when you are attacked by a pathogen, and passive immunity occurs when you receive antibodies from a different source, such as infants from their mother. The lymphatic system is also part of the immune system and involves a network of lymphatic vessels and lymph nodes that contain a clear fluid called lymph. Lymph helps return fluid to the blood to prevent swelling and to help regulate blood volume and blood pressure. There are clusters of white blood cells within each lymph node, and the lymph nodes become swollen when you fight sickness. When you are exposed to certain pathogens, your immune system remembers those pathogens and builds up antibodies to fight them in the future. From the smallest cut to the deadliest virus, your immune system helps keep you alive every day.
Diagram of the Lymphatic System
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