Why are human veins green while blood is red?

We all know that human blood is red, but the veins under the skin are green. It is due to the light reflection of the skin, the amount of oxygen in the blood and other factors.

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Why are human veins green while blood is red? Picture 1

Human blood is always red due to iron, iron mixed with oxygen in the lungs, causing blood to turn red. Therefore, blood in the body is red or red, depending on the amount of oxygen in the blood. The veins themselves are not green, they are only green when viewed through the skin and are dominated by the following four factors.

The first element is the interaction of light with the skin in multiple wavelengths, equivalent to different colors. Human skin always absorbs light and radiates back into the environment thousands of times in the blink of an eye.

Scientists found that human skin emits more blue light than red, so we often see veins are green.

Why are human veins green while blood is red? Picture 2

In addition, the amount of oxygen transported by red blood cells in the blood affects the color and ability to absorb light of the blood. A red blood cell can transport up to 4 molecules of oxygen. In the process of transport, due to the impact of surroundings such as high temperature, acid environment, one or more oxygen molecules will leave the red blood cells, making the blood more dark and easier to see green.

The diameter and position of veins is also one of the reasons why we see them green. If the veins are located just under the skin, they will be red, but the deeper they go, they will gradually turn blue. In fact, the vast majority of human veins lie more than half a millimeter deep under the skin.

The last factor is the brain . The contrast of the surrounding skin color causes the brain to be "fooled" and tends to make veins green. For example, when you put purple next to red, your brain will turn purple into blue, not purple.