Why are veins blue
The meandering path of the blood through our body is pretty intricate and hard to follow. And, apart from the complicated biological phenomena occurring inside the blood stream, there is another strange little enigma that attracts attention. Veins give off a blue shade, despite the fact that the blood flowing through them is red.
The pumping organ of the body, the heart, pumps blood continuously to the lungs, where the blood becomes oxygenated. Arteries act as the distribution network for the bright red oxygen rich blood to reach the various parts of the body. The tiny capillaries act as the interface between the blood stream and the body tissues. Once the oxygen is soaked out of the blood, it retraces the path through the veins. Though the blood loses some of the brightness in the shade of red, but the fact is that there is no way blood could be blue in color. Actually, there is a different theory behind the peculiar color of the veins that carry red blood, but appear blue. The basic tenet of the theory is the fact that the penetration of light depends upon its wavelength, and blue and red light being of different wavelengths, penetrate the skin to different degrees. The area between the blood vessels and the surface is very shallow. This particular area scatters most of the blue light. On the contrary, the surrounding area sends back a greater amount of red light’s wavelength. Thus, the result is that there is sharp contrast between the color perception of these areas, and we experience the blueness of the veins. Actually speaking, there is no definite blue color of the veins.
It is just that we interpret it to be blue in color because of the relative color of the surrounding skin. This can be established by trying a very simple analysis. Make a slight cut in a white paper sheet and try to place it on the skin in such a way that that the slice is over the vein, that appeared to be blue in color. It is observed that the blue color is no more evident. This proves that it is not any pigment, but a contrast that creates the impression of blue veins in the brain.