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Autoimmune diseases occur when the immune system destroys its own healthy tissues. When this occurs, white blood cells cannot distinguish between pathogens and normal cells.
Human neurons are so small that they require a microscope in order to be seen. However, some neurons can be up to 3 feet long, such as those that extend from the spinal cord to the toes.
Cancer has been around as long as humankind, but only in the second half of the twentieth century did the number of cancer cases explode.
Aspirin is the most widely used drug in the world. It has even been recognized as such by the Guinness Book of World Records.
Most fungi that pathogenically affect humans live in soil. If a person is not healthy, has an open wound, or is immunocompromised, a fungal infection can be very aggressive.