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The average adult has about 21 square feet of skin.
There are 20 feet of blood vessels in each square inch of human skin.
Thyroid conditions may make getting pregnant impossible.
Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.
After 5 years of being diagnosed with rheumatoid arthritis, one every three patients will no longer be able to work.
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