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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.
There are more bacteria in your mouth than there are people in the world.
GI conditions that will keep you out of the U.S. armed services include ulcers, varices, fistulas, esophagitis, gastritis, congenital abnormalities, inflammatory bowel disease, enteritis, colitis, proctitis, duodenal diverticula, malabsorption syndromes, hepatitis, cirrhosis, cysts, abscesses, pancreatitis, polyps, certain hemorrhoids, splenomegaly, hernias, recent abdominal surgery, GI bypass or stomach stapling, and artificial GI openings.
The shortest mature adult human of whom there is independent evidence was Gul Mohammed in India. In 1990, he was measured in New Delhi and stood 22.5 inches tall.
The familiar sounds of your heart are made by the heart's valves as they open and close.