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If Blood Is Red, Why Are Veins Blue?
why is that our veins blue when the blood in it is red?
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Hello friend, first I will ask you a question; Have you seen how iron is oxidized? What color do you see? It's red right!

Now, do you know what the main content of the blood is? They are the erythrocytes. Small blood cells responsible for transporting the oxygen we breathe, through the body more specifically through the blood vessels. The erythrocytes transport oxygen thanks to their internal molecules called Hemoglobins responsible for capturing oxygen.

The hemoglobin has an iron atom in the center, which allows this molecule to capture oxygen. When it is united, what we know as oxidation of the blood is produced, this is when the blood acquires the reddish color.

This happens every time the blood passes from the heart to the lungs where the exchange of oxygen is carried out by carbon dioxide. That is, the blood comes with carbon dioxide from the body and excretes it in the lungs, while the oxygen in the lungs enters the blood and oxidizes it.

This red oxidized blood travels through the arteries, arterioles and capillaries; in the latter, another exchange is made (inverse to the previous one). Blood expels oxygen to the organs and the organs transfer the carbon dioxide produced in cellular respiration.

Now the blood is enriched in carbon dioxide and it travels from the capillaries to the veins, collecting all the carbon dioxide and expelling the oxygen inside the body, and with this the reddish coloration. When united with CO2, it loses its red color and turns violet. When mixed with more debris, along with the skin type of the person and the effects of light on it, it resembles a more bluish color.

I hope I have helped in your doubt, happy night

$2.09
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Thus, veins convey deoxygenated blood from tissues to the heart, the special case being aspiratory and umbilical veins.

However, veins don't seem blue since they are conveying deoxygenated blood.

Human blood = red (or a few shades of red like deoxygenated blood being darker especially maroon)

I am stating human blood, since we utilize iron to tie oxygen dissimilar to lobsters, creepy crawlies who have copper as their primary oxygen receptor in this way giving their blood a blue shading.

The red shade of our blood is a direct result of hemoglobin, press and atomic oxygen. This complex principally ingests higher vitality, shorter wavelength blue and green light, deserting basically red wavelength for our eyes to identify.

Blue light gets consumed and scattered on its way through our skin than red light because of the structure of skin and fat tissue.

Veins are near skin surface not at all like oxygenated blood conveying supply routes which are covered somewhere inside tissues. Also, since they are bigger and have more slender dividers, they give the paltform to reflect blue light as it is ingested more than red once it achieves the veins.

And furthermore there is a critical job of our preparing also. The vein region is deciphered bluer in contrast with the encompassing skin by our brains.

The veins with even less skin covering it, seems red, for ex on eyes, on retina ( one is on my cheek ) as there isn't sufficient tissue covering the blue vein impact

$1.01
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Because when you look at a vein you are seeing the blood being diffused by the skin. This is why after having blood drawn or tapping a vein it will change from blue to a dark purple in colour. The vein has become more prominent or engorged and so the amount of red blood is greater and shows through the skin more.

Based on your race and ethnicity your veins might not be blue to begin with, they can appear darker in colour.

$0.85
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Super easy. Blood appears blue because its lack of oxygen. Once blood is exposed to oxygen it will obsorb the oxygen and turns red. 

$0.47
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Ok well there are actually a lot of reasons that have been though up to answer this question, but I've been able to discern which is right and which is wrong.

The reason why veins look blue even though blood is red is simply because of the difference in how the skin let's light pass through it. To actually see an object, light has to fall on it so that your eyes can actually general an image in your retina.

Now in the case of light causing veins to look blue. Firstly, for an image to form in our eyes, or for us to see, light has to be reflected back from that image into our eyes and depending on the wavelength of the light and material thats reflecting it, we perceive different colours. As far as skin goes, it mostly doesn't let much light pass through it, especially blue light and thus reflects almost all light, and that's why people's skin are white (depending on how much melanin they have). Blood on the other hand absorbs almost all light but reflects red light and that's why blood is red.

Veins however are located just under the skin, and at about 0.5mm under the skin, it's mostly red light and blue light that's reflected. Seeing as blue light doesn't pass through skin well, it's reflected. Thus, when you see veins and they appear blue, you'll know it's because vessels under the skin at about 0.5mm of depth don't absorb blue light well, instead they reflect them and it's that reflected light that your eyes pick up and tell your brain that veins are blue.

I hope this helps

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