I am absolutely staggered by the number of people who actually believe that deoxygenated blood is blue.
No, human blood is *never* blue.
Even when totally depleted of oxygen, it becomes a dark red colour (some might call it maroon). If you were to see a car or a paint strip that colour, you would say it was red.
Fully oxygenated (arterial) blood is bright red. Depleted (venous) blood is dark red. NOT blue.
The only time blood is ever blue is in mollusks and some arthropods, which utilize copper in the molecule that carries oxygen to the their tissues (hemocyanin), instead of iron as vertebrates do (hemoglobin).
The veins through your skin only look blue because of diffusion of the light while passing through layers of tissue. In actuality, they're more of a greyish, white colour. You don't normally see arteries through the skin because they tend to be buried deeper in the tissues, but they're pretty much the same colour (but thicker walled, with higher blood pressure).
The idea that human blood is blue is absolutely a myth.
· 1 decade ago