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The familiar sounds of your heart are made by the heart's valves as they open and close.
If all the neurons in the human body were lined up, they would stretch more than 600 miles.
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
Stroke kills people from all ethnic backgrounds, but the people at highest risk for fatal strokes are: black men, black women, Asian men, white men, and white women.
Your skin wrinkles if you stay in the bathtub a long time because the outermost layer of skin (which consists of dead keratin) swells when it absorbs water. It is tightly attached to the skin below it, so it compensates for the increased area by wrinkling. This happens to the hands and feet because they have the thickest layer of dead keratin cells.