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Dear Phil:
Phil, take a look at the underside of your wrist. See anything? I bet you see veins that carry
blood. They look blue, don't they?
The cells in your body need oxygen all the time. How do they get oxygen?
Through the blood which picks up oxygen from your lungs that you breathed in and carries it to
all parts of your body. Then the blood, minus the oxygen, is pumped back to your heart, ready to go
pick up more oxygen in your lungs and start the next trip.
Now there's a special molecule in your blood that makes it possible for your blood to hold
onto oxygen molecules and then release them at the right destination. When your blood is carrying
oxygen, this molecule is bright red and makes your blood look bright, bright red. After this
molecule releases the oxygen, it loses some of its color. It looks darker and purpler, and makes
your blood look purpler -- even blue. Since veins and arteries and blood vessels don't have much
color of their own, they take on the color of what's flowing through them. So, veins look bluish,
while arteries look far, far redder.
Incidentally, did you ever wonder why you can see these bluish veins more easily than you can
see your reddish arteries? Arteries carry blood to your body very quickly and under great pressure
while veins carry the blood back to your heart at a slower pace and under less pressure. Because of
the pressure, an injury to the artery would cause you to lose blood more quickly than loss of blood
from a vein -- and that could be life threatening! Therefore, arteries are buried deeper inside the
body where they are better protected from injury, and veins are closer to the surface of your skin
and more visible. Neat, huh?
Signed,
Wendell
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