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Blood is always red, never blue.

Human Anatomy, Physiology, and Medicine. Anything human!

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What color is deoxygenated blood?

Poll ended at Fri Apr 29, 2005 5:05 am

Red
4
80%
Blue
1
20%
 
Total votes : 5

Postby nsh87 » Wed Oct 31, 2007 4:03 am

"deoxygenated" blood in the body is really only about 75% deoxygenated. when you cut yourself you're still seeing highly oxygenated blood pouring out. i don't know if the oxygen molecules are ever fully released from the hemoglobin as the blood dries....this would be something to find out. if the oxygen stays attached, then at any point you're still really looking at 75% oxygenated blood.
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Postby biohazard » Tue Apr 22, 2008 1:11 pm

The horseshoe crab has blue blood! These odd arthropods have copper-containing protein hemocyanin instead of hemoglobin, and it is indeed blue - although when oxygenated. Although this has nothing to do with human blood, it proves one point: someone earlier in this thread claimed that venous blood turns red because it contacts the air, but this is not the case: hemocyanin turns from colourless or whitish to blue when it contacts air, because it carries oxygen extracellularly. Hemoglobin, to the contrary, carries oxygen intracellularly, and thus the colour doesn't change when you expose it to the air (although on a longer time scale the oxygen saturation changes). And yes, venous blood samples taken with the vacuum method pretty clearly demonstrate that the venous blood is red as well, just darker.

And now, I have revived a funny thread from the past with a horseshoe crab! Yey!
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Re: Blood is always red, never blue.

Postby MrMistery » Tue Apr 22, 2008 8:37 pm

What does it have to do whether the pigment is in cells or not? Hemoglobin and other pigments need to be locked inside cells because it is too small and it would clog the excretion systems(be they nephridia, nephrons or whatever). Hemocyanin and other pigments are large enough to float around in the plasma/hemolymph with no ill effects on the excretory system.
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Re: Blood is always red, never blue.

Postby biohazard » Wed Apr 23, 2008 5:53 am

It has to do with the fact that hemocyanin changes its colour right after it contacts the air, whilst hemoglobin, being intracellular, doesn't react instantly unlike someone wrote in a reply in this thread, where they claimed that venous blood is blue and that it turns red because it contacts the air :)
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Re: Blood is always red, never blue.

Postby arangojf » Fri Feb 26, 2010 9:56 pm

Hey, you bunch of know-it-alls, the name of the thread is "Blood Is Always Red, Never Blue", and it started off completely informational until it turned into a ***

Keep it humble, ***. And you, MrMistery, while I have nothing against looking like a douche, I do frown upon looking, typing, and thinking like one all at once. Stop hugging up all the douche! If you're going to make a point that calls the casual learner "moronic", make sure you at least spell "hemoglobin" right.

I didn't know blood wasn't blue in the veins, and thanks to the original post, I learned something new. I also learned you're a ***.

Koniek, ***,

Jhon
Last edited by JackBean on Sat Feb 27, 2010 2:52 pm, edited 1 time in total.
Reason: be polite on this forum!
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Re: Blood is always red, never blue.

Postby Muzammil » Sat Mar 13, 2010 8:53 pm

But what if when some one throws a fist at our eye, it turns blue? Is it because the veins are damaged and oxygen composition is reduced because thats when the deoxygenated blood accumulates.
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Postby biohazard » Mon Mar 15, 2010 7:09 am

The "black eye" happens because the red blood cells that form the hematoma after a hit start slowly breaking down and the products of this breakdown event are colourful (from bluish to green/brown depending on the timepoint). To be more precise, it is mostly the breakdown of hemoglobin that causes the colours. But initially after the hit the eye is just swollen because of the burst vessels and the blood is red as usual.
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Re: Blood is always red, never blue.

Postby HolidayInnDoctor » Sat Apr 24, 2010 1:02 pm

Suppose skin acts like the reverse lens that is being discussed in the news currently and that is why blood looks blue throught the skin of an alive person whose skin is whatever percent water.
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Postby Vampire11 » Tue Oct 12, 2010 10:19 am

I almost went insane in my science class, okay i'm young and i don't know much but at leasti have the brains to knoow that bloood is red!!!
a few of the students in my class told me that blood was blue until it came out of your veins, now this i could handle beucase they're all morons but then the teacher came over and i asked him to correct them he then said to me
"they're correct grace" then the entire class started to laugh at me!
so now they think i'm the idiot!!!
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Postby mohbio » Thu Nov 11, 2010 12:35 pm

I do think that red blood cells are red because of hemoglobin combined with oxygen,but when it is combined with carbondioxide,it will be dark red not blue
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Re: Blood is always red, never blue.

Postby sara135 » Mon Jul 11, 2011 2:12 pm

Blood is never ever blue!! Oxygenated or deoxygenated, it is NEVER blue! Just a common myth. Deoxygenated/venous blood is a dark, crimson red while oxygenated/arterial blood is a brighter red. Never black, blue, green, whatever other color. It's always red. Sometimes a different shade of red, but it's always red. Veins look blue because of the way your eyes perceive the color and the way light reflects. Veins are not actually blue, they’re white-ish.
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Re: Blood is always red, never blue.

Postby zanebo » Sun Sep 11, 2011 5:06 am

This is for you who think blood is blue when deoxygenated. Explain to me why blood taken from a vein, that is caring deoxygenated blood to the heart, and collected in a test tube that is vacuum sealed is brick red in color. The blood leaving the vessel is not receiving any oxygen when it enters the tube due to the fact that the test tube is vacuumed seal (no O2 in tube).
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