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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.
Adolescents often feel clumsy during puberty because during this time of development, their hands and feet grow faster than their arms and legs do. The body is therefore out of proportion. One out of five adolescents actually experiences growing pains during this period.
The heart is located in the center of the chest, with part of it tipped slightly so that it taps against the left side of the chest.
The human body produces and destroys 15 million blood cells every second.
In 1864, the first barbiturate (barbituric acid) was synthesized.