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Only one in 10 cancer deaths is caused by the primary tumor. The vast majority of cancer mortality is caused by cells breaking away from the main tumor and metastasizing to other parts of the body, such as the brain, bones, or liver.
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.
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.
On average, someone in the United States has a stroke about every 40 seconds. This is about 795,000 people per year.
Pubic lice (crabs) are usually spread through sexual contact. You cannot catch them by using a public toilet.