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Alzheimer's disease affects only about 10% of people older than 65 years of age. Most forms of decreased mental function and dementia are caused by disuse (letting the mind get lazy).
Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.
The Babylonians wrote numbers in a system that used 60 as the base value rather than the number 10. They did not have a symbol for "zero."
The human body's pharmacokinetics are quite varied. Our hair holds onto drugs longer than our urine, blood, or saliva. For example, alcohol can be detected in the hair for up to 90 days after it was consumed. The same is true for marijuana, cocaine, ecstasy, heroin, methamphetamine, and nicotine.
Blood is approximately twice as thick as water because of the cells and other components found in it.