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Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.
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.
More than 2,500 barbiturates have been synthesized. At the height of their popularity, about 50 were marketed for human use.
Calcitonin is a naturally occurring hormone. In women who are at least 5 years beyond menopause, it slows bone loss and increases spinal bone density.
Recent studies have shown that the number of medication errors increases in relation to the number of orders that are verified per pharmacist, per work shift.
![Urinalysis. During a simple urinalysis, a stick with colored blocks is dipped into a urine specimen.](https://biology-forums.com/gallery/47/medium_14755_26_10_12_5_21_07_96732306.jpeg)
![John Lewis Krimmel’s painting of the Fourth of July in Centre Square Philadelphia (1812) shows the d](https://biology-forums.com/gallery/47/medium_374628_16_08_15_9_59_55_222732435.jpeg)