Is Blood ever Blue?

I'm so confused! my anatomy teacher says blood is never blue, it becomes a dark red color when it becomes deoxygenated . The blue-green color we see through our veins are a poor reflection of light to make then appear to be blue for the outside of our skin. Okay understandable. But, when I read about Cyanosis which is a blue discoloration of the skin due to oxygen deprivation, it says that the blue hue of the skin comes Blue deoxygenated blood. This is confusing. Can anyone shed some light??? And if so, can you give me a web site?

Is Blood ever Blue?
It seems the old misconception that blood is blue when it is deoxygenated will never die.





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.





It is impossible to turn haemoglobin blue.
Reply:Im confused i was taught blood was blue in your body but as soon as oxygen hits the blood it turns red.... here is some more info i found:





In humans and other hemoglobin-using creatures, oxygenated blood is bright red. This is due to oxygenated iron-containing hemoglobin found in the red blood cells. Deoxygenated blood is a darker shade of red, which can be seen during blood donation and when venous blood samples are taken. However, due to skin pigments, blood vessel coverings and an optical effect caused by the way in which light penetrates through the skin, veins typically appear blue in color. This has led to a common misconception that venous blood is blue before it is exposed to air. Another reason for this misconception is that medical charts always show venous blood as blue in order to distinguish it from arterial blood which is depicted as red on the same chart. The rare condition sulfhemoglobinemia results in green blood.





The blood of horseshoe crabs is blue, which is a result of its high content in copper-based hemocyanin instead of the iron-based hemoglobin found, for example, in humans. Skinks in the genus Prasinohaema have green blood due to a buildup of the waste product biliverdin.





i found this on wikipedia: http://en.wikipedia.org/wiki/Blood
Reply:yes,sometimes
Reply:my teacher informed me that blood was blue inside of the veins because it is full of carbon dioxide and has not been in contact with oxygen





interesting huh?
Reply:First up - all (human!) blood is red. Blood in arteries is bright red, since the haemoglobin molecules (which largely give the blood its colour) are mostly bound to oxygen. In veins, much of the oxygen has moved off into the tissues, and the deoxygenated haemoglobin molecules are consequently a darker red... but STILL red.





Then why do veins appear blue?





The first thing to understand about the physics is that blood usually absorbs almost all of the light that hits it - although it does reflect a little red light, which is obviously why blood appears red.





Secondly, different wavelengths of light have different likelihoods of be scattered. (In completely non-physicist's terms, light scattering occurs when a wavelength of light hits an atom, is absorbed by the atom, and then expelled again in a different direction. This isn't quite right, but it'll do as an explanation.) As it turns out, wavelengths towards the blue side of the spectrum are much more likely to be scattered than those near the red side.





Now, when the light passes through the skin, the blue light is therefore preferentially scattered. Some of it reaches your eye. The red light is less scattered (less reaches your eye), and most of it reaches the blood... where it is promptly absorbed. So virtually none of it reaches your eyes.





And thus, since basically only the blue light reaches your eyes, the vein appears blue. A similar thing happens in cyanosis - here the blood is more deoxygenated than usual, which would make it a darker red than normal. But, seen through the skin / nails / mucous membranes it looks a deep purple / blue colour.





A great website that explains the "blue blood" phenomenon in more detail is here: http://discovermagazine.com/1996/dec/the...





Hope that helps!