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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.
Many people have small pouches in their colons that bulge outward through weak spots. Each pouch is called a diverticulum. About 10% of Americans older than age 40 years have diverticulosis, which, when the pouches become infected or inflamed, is called diverticulitis. The main cause of diverticular disease is a low-fiber diet.
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.
Human kidneys will clean about 1 million gallons of blood in an average lifetime.
There are more nerve cells in one human brain than there are stars in the Milky Way.