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Human kidneys will clean about 1 million gallons of blood in an average lifetime.
There are more bacteria in your mouth than there are people in the world.
The familiar sounds of your heart are made by the heart's valves as they open and close.
Egg cells are about the size of a grain of sand. They are formed inside of a female's ovaries before she is even born.
In 2012, nearly 24 milliion Americans, aged 12 and older, had abused an illicit drug, according to the National Institute on Drug Abuse (NIDA).
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