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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.
The ratio of hydrogen atoms to oxygen in water (H2O) is 2:1.
Vaccines prevent between 2.5 and 4 million deaths every year.
Only 12 hours after an egg cell is fertilized by a sperm cell, the egg cell starts to divide. As it continues to divide, it moves along the fallopian tube toward the uterus at about 1 inch per day.
The U.S. Preventive Services Task Force recommends that all women age 65 years of age or older should be screened with bone densitometry.