Why Do Veins Appear Blue in Color?

Nicks J Apr 17, 2019
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When the blood circulating through the veins is red, why does the color of these blood vessels appears blue? Learn more...

Did You Know?

It is not the color that really differentiates the arteries from the veins. From an anatomical point of view, the arterial wall is found to be thicker than the venous wall.
Have you ever examined your wrists closely? If you have done that, you must have observed a number of blue veins passing from your wrists to the fingers. Veins do an important job of transporting impure (deoxygenated) blood to the heart, where it is oxygenated to get rid of all the impurities.
Now, when red-colored blood is flowing through the veins, how come the color is blue? Some argue that veins carry deoxygenated blood, which is the reason behind the blue color. However, this is not true, as the color does not alter with the purity of blood. It remains red throughout.

Why Do Veins Look Blue?

The color of any object is determined by the color of light reflected from it. As we all know, sunlight or white light is made up of 7 different colors, some of which are absorbed, while others are diffused by the object. The colors dispersed are perceived as the color of the object.
For instance, bananas appear yellow as all the colors except yellow are retained without reflection. To put it simply, only yellow color is dispersed from the bananas to our eyes, which is why we consider them to be of yellow color.
Similarly, in case of veins, when light falls on the skin and hits the veins, all the colors except blue are absorbed by the skin. In other words, only blue color is sent back, while the rest are absorbed by the skin. So, despite carrying red blood, the reflection of blue color from veins is what makes them appear blue.
Also, blue light has a higher frequency in comparison to that of red, green, orange, or yellow light. Higher the frequency, higher will be the energy of particle matter, hence, more will be the depth of penetration. Also, shorter the wavelength (as in case of blue light), greater will be the possibility of getting reflected.
Hence, the blue light easily passes through the skin, strikes the veins, and is diffused back. Other colors are unable to penetrate the skin, and so, get easily absorbed. Blue light, with higher penetration potential, is the only one that reaches the veins and subsequently bounces back and reaches our eyes. That is why the color of the veins appears blue.
If blue is not the actual color of veins, then what's their true color? Arteries and veins, although transport oxygenated and de-oxygenated blood respectively, have no significant difference in color, both are reddish-brown in color. Upon dissecting the skin, you will encounter veins that are dark red in color, while arteries would appear bright red.
Disclaimer: The information provided is solely for educating the reader. It is not intended to be a substitute for the advice of a medical expert.
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