The blood inside a human is blue until it meets oxygen then it turns red. What other creatures on Earth can say the same thing?

star_gazer

Actually, human blood is never blue. Blood is a bright red in its oxygenated form (i.e., leaving the lungs), when hemoglobin is bound to oxygen to form oxyhemoglobin. It's a dark red in its deoxygenated form (i.e., returning to the lungs), when hemoglobin is bound to carbon dioxide to form carboxyhemoglobin. Veins appear blue because light, penetrating the skin, is absorbed and reflected back to the eye. Since only the higher energy wavelengths can do this (lower energy wavelengths just don't have the *oomph*), only higher energy wavelengths are seen. And higher energy wavelengths are what we call "blue." http://www.straightdope.com/columns/read/1419/if-blood-is-red-why-do-your-veins-look-blue Jan 01 11, 1:50 AM

author

Human blood is red, ranging from bright red when oxygenated to dark red when not. It owes its colour to hemoglobin, a metalloprotein compound containing iron in the form of heme, to which oxygen binds. There exists a popular misconception that deoxygenated blood is blue and that blood only becomes red when it comes into contact with oxygen. Blood is never blue, but veins appear blue because light is diffused by skin. Moreover, the blood inside is dark red and exhibits poor light reflection. From a physiological perspective, veins and arteries appear similar when skin is removed and are seen directly. http://www.biology-online.org/biology-forum/about763.html Jan 02 11, 6:46 PM

Baloo55th

Blood looks blue in surface veins, but that's probably down to coloured light filtering by the skin. Where the idea of 'blue blood' in aristocrats came from, I don't know. They lost enough red blood publicly on battlefields and at executions... Jan 03 11, 7:47 AM