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The familiar sounds of your heart are made by the heart's valves as they open and close.
Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.
Liver spots have nothing whatsoever to do with the liver. They are a type of freckles commonly seen in older adults who have been out in the sun without sufficient sunscreen.
About 60% of newborn infants in the United States are jaundiced; that is, they look yellow. Kernicterus is a form of brain damage caused by excessive jaundice. When babies begin to be affected by excessive jaundice and begin to have brain damage, they become excessively lethargic.
Bacteria have flourished on the earth for over three billion years. They were the first life forms on the planet.