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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.
The average older adult in the United States takes five prescription drugs per day. Half of these drugs contain a sedative. Alcohol should therefore be avoided by most senior citizens because of the dangerous interactions between alcohol and sedatives.
The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
Pubic lice (crabs) are usually spread through sexual contact. You cannot catch them by using a public toilet.
Egg cells are about the size of a grain of sand. They are formed inside of a female's ovaries before she is even born.