My science teacher argues that if our blood was blue, or faces would turn blue when we blush...?

Is it true that blue blood is just a myth and that or veins are actually blue?My science teacher argues that if our blood was blue, or faces would turn blue when we blush...?
(Sorry I answered a similar question in a previous post, so I didn't want to go and type everything out again...my keyboard is missing 5 keys so it is hard to type, so I am just copying my previous answer).





TRUTH: (and concrete facts)


Oxygenated blood is bright red (found in arteries).


Deoxygenated blood is dark red, almost purple (found in veins).





Before you go on believing blood is blue in the veins please read: http://en.wikipedia.org/wiki/Blood#Hemog鈥?/a>





Someone pointed this out to me a while ago when I thought it was blue.





The 'hemoglobin' without the oxygen 'appears' blue because the iron atom in the heme group is not oxidized. When it is oxidized it changes the configuration of the porphyrin moiety of hemoglobin to which the iron is bound. This change causes the blood to appear bright red, instead of it's normal dark red.


This change in color is a result of how a different configuration of the porphyrin moiety in the red blood cell reflects a slightly different wavelength of light.


http://en.wikipedia.org/wiki/Hemoglobin#鈥?/a>





Hope that clears things up.My science teacher argues that if our blood was blue, or faces would turn blue when we blush...?
Every time this question is asked, I give the same response. A simple test. If blood is drawn from your veins, say for a donation or for a blood test, you can simply look at the color. You can watch it run through a tube during a blood donation (in the total absence of air once the blood starts flowing) and see it exactly as it looks in a vein. It will always be red. A dark, dark red. It will never be blue.
It seems likely. Through my skin now I can see blue veins and I know from experience that when the deoxygenated blood is taken from them (I try to give blood regularly) it comes out red. Probably still some oxygen in there, but evidence we don't have blue blood. Darn all those diagrams showing blue for blood returning to the heart.





However, if blood lacks oxygen or gets pulled from the tissue we do get a bluish tint. There is in fact a condition called methemoglobinemia that reduces the bloods ability to carry oxygen and causes the sufferers to turn blue. There was an clan in Kentucky that had a genetic abnormality that gave them this condition. What's surprising is that they were reportedly (in what little I read) no less healthy than most people. Though I suppose marathon running was likely out for them.

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