If Our Blood is Red, Then Why do Veins Appear Blue?

If blood is red, and we bleed red whether it’s for a lover or whether it’s for lab tests, then why are the veins on our wrist and ankles appear blue?

The blue color is less in the environment, that is there are literally no animals of blue color. Except for one butterfly and frog who are not actually blue but seem blue because of tiny bone structures. Blue is a very rare color, just like the sky and ocean are in nature(that is also because of refraction of White Light). Yet it can be seen in us, the Humankind. In this evolved Homo Sapiens, from apes, there is this blue color, but is it really there? Let’s find out.

Have you ever wonder about that!

Via: Youtube

Yes, that’s true we have both veins and arteries. But we don’t bleed out from our arteries (we do, but in a lab test and stuff). It’s the veins and that blue thing is definitely nor poison neither it is water. (If you think the body is made up of 70% water that is not the case either). If you are going dark or considering yourself Lord Shiva ( if you get my bad pun). So, coming back to the point, why veins are blue?

Blood is always red. Actually, veins look blue because light penetrate through the skin and illuminates the veins. White light (from the sun) penetrate with different degrees of success. What makes it back to your eye is the blue light.

Let’s find out the Actual Reason :

When someone asks the question “Why are veins blue?” a likely response is that they’re blue because the blood in the veins is de-oxygenated. Which is certainly accurate, but not the perfect truth that veins carry a lower concentration of oxygen-rich blood than their arterial counterparts, this still isn’t the reason for their bluish appearance in our skin.

Via : amp.businessinside

Usually people react to blue vein concept by assuming that it is caused by de-oxygenated-blood and then wrangle with the statement that “I’ve never seen blue blood ever before” one might then hear the slightly more revealing and little legit but increasingly far-fetched claim that we don’t ever observe blue blood because it is immediately oxidized upon contact with air. (Check out these beautiful  Yahoo Answers to witness these arguments yourself with all due pleasure.)

Wrong. Blood is never blue. Duh. Ever. Period. (And, this is an ideal example of why you should not ingest information from Yahoo Answers uncritically.)

The Concept of White Light :

Via: khanacademy

The bright red color of arterial blood stems from a complex that’s formed between iron, haemoglobin and molecular oxygen. This complex mainly absorbs shorter wavelength ( higher energy) blue and green light, leaving behind primarily just red wavelengths for human eyes to detect.

However, even when blood is largely exhaust of oxygen, it is never blue: it’s more of a deeper red or maroon color. And, although I have not engaged in surgery. But those who have participated in surgery did assure that in surgery, veins within the body never appear blue either. So, not just blood but, veins on their own aren’t blue either. “Blue Veins” are a unique phenomenon to the skin.

Via: ytimg

The most elementary answer that can be given is that physically and stem directly from the way in which light interacts with blood (how it is absorbed) and with skin (in this case, how light is reflected). And one of the many other reasons for blue appears can be psychological, dealing with the way in which our brain processes information relatively to generate color perception.

The heart pumps blood to lungs, which picks up the oxygen-rich blood. The oxygen-rich blood is pumped out to various body parts through arteries. It’s bright red at this point. From arteries, the blood flows through tiny blood vessels known as capillaries. Here, the capillaries give up its oxygen to the body’s tissues. (Your lips have a lot of these capillaries, which is why they’re red). Now, the de-oxygenated blood returns back to the heart, through veins. This blood is darker in color but not blue. So, de-oxygenated blood is not any reason.


Via : everydayhealth

The reason why only veins appear blue and not arteries are that veins are the only vessels we actually observe through the human skin. This is due to the fact that veins have thinner walls, are larger, and are more superficial than arteries. (medically speak for closer to the surface). All of these aspects of veins have clear biological rationales.  The primary function of the venous system is as a blood reservoir, which is beyond just carrying blood back to the heart.

In fact, about two-thirds of our blood volume is held in our veins at any given time, hence their larger size. The heart pushes blood directly through the arteries, therefore, blood flows with much higher pressure, thus walls of arteries are thicker than that of veins.

via: Health Line

Finally, veins play an important role in heat exchange with the outside environment which helps to cool down the body. Hence, they are located closer to the surface of the human skin.  Arteries can also perform the similar function, but it’s much more superior to keep those higher pressure blood conduits deeper in the body and protect them from injury.

The take-home message here is that the bluish appearance of veins in the skin has everything to do with the thickness of skin, the light phenomena along where they are located which have nothing to do with the concentration of oxygen within them. In fact, if we could see them through the skin as well, even arteries would look blue because of the phenomena of light.

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