The Smurfs Among Us

The human body is fascinating. Previously we had discussed about the human eye, and yesterday, we discussed the origins of the Adam’s apple. Today, as indicated by the title, we look at colour. Specifically:

Why Are Veins Blue?

As opposed to what many people are led to believe, it is not due to the colour of our blood. Oxygenated blood is bright red in colour, whereas deoxygenated blood is dark red. Anyone who has had his blood taken out for testing, or donated blood, can attest to that. The veins themselves are also not blue (they are mostly transparent). Then why?

Turns out, it is optical. As mentioned in this paper by Alwin Kienle et al, the blood in your veins appear blue because you are looking at them through layers of skin and fat. Our skin scatters the bulk of red light and leaves just the blue light to be reflected off the blood in our veins. It is similar to how the sky appears blue and how the setting sun appears red.

When I was small, I was led to believe that deoxygenated blood is blue in colour. The first time I donated blood, I realized that is not the case. Thus, I was left to deal with this question. Thought some of you may also have the same misconceptions.