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Q & A

Q Why is the tip of your fingernail white and the rest is not?

A Let's peek in the, uh, nail file and, uh, polish this off. Fingernails start out colorless and see-through. Most of the nail looks pink because the skin below has lots of blood vessels. Fewer blood vessels are found near the start of the nail, so that part looks whitish. At the end of the finger, the transparent nail turns white after being exposed to the air.

Q What causes swelling of a body part due to an injury?

A When cells are damaged, they give off chemicals that make nearby blood vessels get bigger. So more blood flows into the area, making it redder and warmer. As the blood vessels get bigger, the blood fluid, called plasma, has an easier time moving out of the vessels and getting to nearby cells. Together, this extra blood and plasma make the area swell. They also bring cells and chemicals to stop any bleeding, antibodies to fight infection, food and oxygen. White blood cells can also move out of the blood vessels to eat up germs and any dead body cells.