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Approximately 500,000 babies are born each year in the United States to teenage mothers.
More than 150,000 Americans killed by cardiovascular disease are younger than the age of 65 years.
The familiar sounds of your heart are made by the heart's valves as they open and close.
The average human gut is home to perhaps 500 to 1,000 different species of bacteria.
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.
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