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The U.S. Preventive Services Task Force recommends that all women age 65 years of age or older should be screened with bone densitometry.
The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
Bacteria have flourished on the earth for over three billion years. They were the first life forms on the planet.
Blood in the urine can be a sign of a kidney stone, glomerulonephritis, or other kidney problems.
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.