What's the reason the skin looks blue when having cyanosis? What's the relationship between lack of oxygen of the bluish appearance?
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Have you thought about the coloring of arterial and venous blood? – Bryan Krause Jul 05 '20 at 01:09
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Yes, and it still doesn't explain to me the bluish colour. (lack of red doesn't mean blue) – Ubiquitous Student Jul 05 '20 at 01:35
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What color is venous blood? – Bryan Krause Jul 05 '20 at 02:16
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Darker red than the arterial one. – Ubiquitous Student Jul 05 '20 at 02:21
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1@UbiquitousStudent No, it's not simply darker red. It has a purplish hue, and to make purple you mix which two colors? – Carey Gregory Jul 05 '20 at 04:06
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- I held many tubes with venous blood, and I didn't notice purplish hue. (See also here: https://en.wikipedia.org/wiki/Blood#/media/File:Venous_and_arterial_blood.jpg) 2. Red and blue give purple. Where this blue comes from?
– Ubiquitous Student Jul 05 '20 at 04:14 -
Advertising my answer about pulse oxymetry which touches on the different absorption of oxy-Hb (oxygenated, arterial blood) and desoxy-Hb (desoxygenated, venous blood) – Narusan Jul 05 '20 at 09:29
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Please, explain the relationship between the cyanosis colour to your answer. Thank you – Ubiquitous Student Jul 05 '20 at 11:48
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@UbiquitousStudent Doesn't really make sense to consider the color of venous blood after it's been exposed to oxygen... – Bryan Krause Jul 06 '20 at 16:40
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Any blood of living human exposed to oxygen... otherwise he'll not be alive. – Ubiquitous Student Jul 06 '20 at 16:54
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@UbiquitousStudent You realize that venous blood has had the O2 it once carried stripped away, right? And although colors are a subjective thing difficult to describe precisely, venous blood does indeed have a purple hue to it as noted by many observers throughout history. – Carey Gregory Jul 07 '20 at 14:29
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The skin of a caucasian-skinned person with cyanosis is described as bluish, but it is still more reddish than blue. The bluish jumps out at us in comparison with healthy well-oxygenated blood.
The colors we see are the product of the incoming light, and the proportion of the wavelengths that are absorbed, scattered, or reflected. Because skin and arteries/capillaries/veins are translucent, there's normally quite a bit of red light scattering and reflection going on. However when looking at veins or cyanotic skin, there's less reflection of the red wavelengths, and the skin looks darker and bluer than we're used to.
If you look at a photograph of someone with Raynaud's or cyanotic hands, you'll see that there's still quite a bit of red!
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This may partly explain why we see different colors, but it doesn't answer the question of why cyanosis causes those changes to occur. – Carey Gregory Sep 24 '20 at 23:41