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Human neurons are so small that they require a microscope in order to be seen. However, some neurons can be up to 3 feet long, such as those that extend from the spinal cord to the toes.
On average, someone in the United States has a stroke about every 40 seconds. This is about 795,000 people per year.
People who have myopia, or nearsightedness, are not able to see objects at a distance but only up close. It occurs when the cornea is either curved too steeply, the eye is too long, or both. This condition is progressive and worsens with time. More than 100 million people in the United States are nearsighted, but only 20% of those are born with the condition. Diet, eye exercise, drug therapy, and corrective lenses can all help manage nearsightedness.
There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
There are approximately 3 million unintended pregnancies in the United States each year.