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Blood in the urine can be a sign of a kidney stone, glomerulonephritis, or other kidney problems.
The familiar sounds of your heart are made by the heart's valves as they open and close.
Human kidneys will clean about 1 million gallons of blood in an average lifetime.
The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
The first documented use of surgical anesthesia in the United States was in Connecticut in 1844.
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