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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.
Parkinson's disease is both chronic and progressive. This means that it persists over a long period of time and that its symptoms grow worse over time.
Pubic lice (crabs) are usually spread through sexual contact. You cannot catch them by using a public toilet.
More than one-third of adult Americans are obese. Diseases that kill the largest number of people annually, such as heart disease, cancer, diabetes, stroke, and hypertension, can be attributed to diet.
After a vasectomy, it takes about 12 ejaculations to clear out sperm that were already beyond the blocked area.