By now you’ve probably heard all about how your veins work. The reason your veins appear blue is because your blood is blue, right? Apparently, your blood is blue until it touches oxygen, which oxidizes it much like it would to rust, turning it red. That would explain why blue veins yield red blood when you bleed, since it’s exposed to the air.
Not sure where this rumor started, but it isn’t even close to the truth.
The Truth about Blue Veins
If blood is always red, then why are veins blue? Well, we can dispel that myth real easily…because your veins aren’t even blue, either. Wait, what? Then why do they look blue? The answer to that question isn’t a biological one, but rather a physics one.
When you look at the veins in your skin, they look blue…sort of. The reason for this is because a certain amount of light has to penetrate your skin for your veins to be properly represented. Since blue and red light are from two completely different wavelengths, the amount of success to which your eyes receive this light information varies greatly. The blue light typically reaches your eyes at a greater volume.
Simply put, since your veins are covered, they appear blue due to how dark it is under layers and layers of skin. Interesting, right?
But since the blood oxygen argument makes a tad bit of sense, is there actually some validity to that argument?
Oxygen and blood
Yes, oxygen changes the color of your blood, but it happens long before you bleed it out. Your heart is constantly pumping blood throughout your body, to different organs that just do different things.
Lungs might be in the biggest need of blood supply, due to how big they are and how hard they work. But blood gets something out of the deal, too.
Your entire body needs oxygen, not just your lungs. It’s the job of the blood to carry that oxygen to other areas of the body. This oxygen-rich blood is, in fact, a different color: bright red, versus the un-oxygenated dark red.
The arteries pump the oxygen-rich blood through the body and into the capillaries. The capillaries, which are much smaller, carry the oxygen blood to very specific parts of the body, handing over the oxygen. The blood then renders itself back to its darker, crimson color and goes back to the heart.