luplodw

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So yesterday in my physiology class we were talking about blood. My teacher said that deoxygenated blood is blue because when oxygen binds to hemoglobin it turns it red. I always thought this wasn't true!! I looked it up online and it said that blood is darker when its deoxygenated but not blue. What the heck? Is my teacher wrong?

Have you had teachers tell you wrong info before?
 

VeganSoprano

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If deoxygenated blood were blue, then blood drawn for routine lab work or blood donation would be blue. Pretty much all of us has had one of these things done. The blood is dark red. Veins look bluish, but they don't just get their color from the blood.
 

heylodeb

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In anatomry textbooks, they differentiate between oxygenated and deoxygenated blood and vessels by coloring them red and blue - maybe she was just referring to drawings or illustrations?
 

luplodw

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Nope he said that when you draw blood or get cut, blood from the veins (deoxygenated) comes in contact with the air (contains O2) so it appears red. When it's in the veins it's still blue. So yeah he wasn't referring to the textbook....so weird...
 

PrimalMU

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I think its more appropriate to say deoxygenated blood is blue-er. It's probably more of a dark purplish. Looking at a vial of blood that has just been drawn doesn't really give you much perspective. Think about it, what color does blue dye look like when it is in the bottle? Usually black. However, when it thins out its blue. Same concept. The real test would be to somehow take veinous blood and, in an oxygen free environment, put some on a slide and put a cover slip over it.

But yea, deoxygenated blood is blueish. Just look at cyanosis, or even the color of veins under your skin.
 

StartingoverVet

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"During a sustained reduction in circulatory supply, the oxygen levels in the tissues decline and under these conditions hemoglobin releases oxygen and turns a much darker red. Seen from the surface, the skin then takes on a bluish coloration called cyanosis"

from Martini & Nash, Anatomy and Physiology.

A slight phrasing problem for your prof between the blood is blue and the blood appears blue.

By the way, I believe that as soon as you draw blood into a syringe it is mixing with oxygen so it probably has already been oxygenated and the color changed back to normal.
 

eventualeventer

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Nope he said that when you draw blood or get cut, blood from the veins (deoxygenated) comes in contact with the air (contains O2) so it appears red. When it's in the veins it's still blue. So yeah he wasn't referring to the textbook....so weird...
Blood tubes contain a vacuum (at least partial), and a syringe with no air in it also does not put blood in contact with air when you are drawing blood, so that's kind of a weird thing to say. StartingOverVet, even when you put just the needle in the vessel without a syringe and let it drip to check whether you are in the artery or the vein, arterial blood looks brighter than venous blood. I have seen a vet accidentally put a catheter into the carotid artery by going through the jugular. Also, if you were oxygenating the blood as you pulled it up with a syringe or a needle and blood tube, how would we ever get meaningful results from arterial blood gas draws?

PrimalMU, even getting venous blood with a capillary tube and sealing it does not make the blood look blue.

Veins in a light-skinned persons body appear blue because of the absorption of shorter wavelengths by the skin and tissues between your eye and the blood.
 

PrimalMU

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After further research, it seems I was half wrong. Deoxygenated blood is very dark red (maybe purplish?). Apparently, veins appear blue due to the wavelength of light. Red light doesn't penetrate tissue as well as blue light does (for the same reasons water is blue), so the veins appear blue. How this is applied to conditions like cyanosis I have no clue.
 

AbbyNormal

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After further research, it seems I was half wrong. Deoxygenated blood is very dark red (maybe purplish?). Apparently, veins appear blue due to the wavelength of light. Red light doesn't penetrate tissue as well as blue light does (for the same reasons water is blue), so the veins appear blue. How this is applied to conditions like cyanosis I have no clue.
well crap

One moment I think I know and the next moment I know not. :(

I've gotta go do farm chores before my horse starts to pout because his dinner is late. Y'all figure it out and I'll catch up to you later.
 

BlacKAT33

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thanks for teaching me something today! im glad my day wasnt a complete waste of time lol
 

VeganSoprano

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Venous blood is also not completely deoxygenated. If you run a venous blood gas panel, you'll get an O2 saturation of somewhere around 80-85, if I'm remembering correctly. This is compared with somewhere in the upper 90's for an arterial sample.
 

heylodeb

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I'm going with the "teacher is wrong" idea. Honestly, they probably heard that from one of their professors and have just passed it down to you. Let's all continue the cycle and go into our clinics tomorrow and tell the clients that their pets blood is blue. :) ok..maybe not...but it'd be funny...:D
 

heylodeb

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had another thought - maybe it IS actually blue if it's COMPLETELY deoxygenated. If all those happy Hemoglobin's drop their O's - it ends up blue. We just never see that case unless a patient in practically dead??? hmm.... who wants to create a study so that we can run our own SDN test?
 
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eventualeventer

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Hmmm, we'd need a sample of blood, some sort of oxygen-poor environment (pure nitrogen from liquid nitrogen? I'm sure there are ways), and presumably a way to mix the blood so that it all got exposed to the O2-poor air. Anyone have a physics geek friend who could find some liquid nitrogen?

just cause I'm a geek (and proud of it)
 

katryn

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I seem to remember this arguement cropping up in my biochem class when we studied hemoglobin and it's O2 and CO2 affinities. My professor never did give us a full answer other than to point out that even venous blood is partially oxygenated.....so I'm guessing that it's more accurate to say venous blood is "more blue" or that arterial blood is "more red" than the other type.
 

Tobysgirl81

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After further research, it seems I was half wrong. Deoxygenated blood is very dark red (maybe purplish?). Apparently, veins appear blue due to the wavelength of light. Red light doesn't penetrate tissue as well as blue light does (for the same reasons water is blue), so the veins appear blue. How this is applied to conditions like cyanosis I have no clue.
For a board full of geniuses sometimes you guys make me wonder...

Cyanosis, while an indicator of things generally "going bad" - shock, drug reaction, ineffective respiratory efforts, etc - it overall indicates that blood is not being appropriately oxygenated. This poorly oxygenated blood is present in tissues that should normally be filled with red, fully (or at least more so than it is) oxygenated blood which is what causes the change in color. Again, the same wavelength principle applies so it appears to be blue rather than red.

While it normally causes cussing in portugese and mild heart palpatations when observed you can for sure tell that something is going wrong when your normally pink gums and tongue turn a lovely shade of lavender, purple or blue :) Sometimes its because you're holding the elongated soft palate patient in a position where they can no longer breathe effectively. Sometimes you give the most wrong drug ever, causing your patient to involuntarily stop breathing. Sometimes your dog decompensates and goes into shock due to some horrific trauma or disease process. Whatever it is, cyanosis is a good indicator that oxygen is no longer binding with hemoglobin, and you should probably remove your elbow from said patient's trachea ;)
 

chris03333

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trust me, I have done quite a few venous cut downs, and I do not hit the veins, venous blood is dark red, not blue.
 

heylodeb

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Whatever it is, cyanosis is a good indicator that oxygen is no longer binding with hemoglobin, and you should probably remove your elbow from said patient's trachea ;)
*smacks palm on forhead*:idea: OHHH. THAT's what I've been doing wrong. mental note, folks: Elbows do not belong in trachea's!!! I learn so much from this forum...:laugh:
hehe
 

parietal

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I actually asked my biochem professor this very question after it came up in anatomy.

He said that if you put venous blood and arterial blood in a spectrophotometer, the venous blood reads as slightly more blue than arterial blood. It's just not really visible to us.

To prove my nerdiness, I've always wanted to try this... :D
 

AbbyNormal

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had another thought - maybe it IS actually blue if it's COMPLETELY deoxygenated. If all those happy Hemoglobin's drop their O's - it ends up blue. We just never see that case unless a patient in practically dead??? hmm.... who wants to create a study so that we can run our own SDN test?
just thinking...

all those patients that were only mostly dead were blue

but once they are fully dead they don't get more blue they are ashen

so assuming it has not been long enough for the blood to pool in the dependent areas why are they not more blue?
 

VeganSoprano

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Yeah...you'll basically never see fully deoxygenated blood that resembles anything we'd recognize by sight as blood.
 

DVMDream

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Venous blood is also not completely deoxygenated. If you run a venous blood gas panel, you'll get an O2 saturation of somewhere around 80-85, if I'm remembering correctly. This is compared with somewhere in the upper 90's for an arterial sample.
80-85 seems kind of high for venous blood gas. Considering the pressure of oxygen at the capillary level and then looking at a normal oxygen-dissociation curve it would seem that venous O2 saturation should be closer to 70 and even that would seem kind of high because the blood has already been passed the tissues and should have released most of its O2 content. I would also assume that venous blood gasses would be lower in animals that are pregnant since the fetus' hemoglobin has such a greater affinity for O2 and the mother's blood is likely to release more O2 from her own hemoglobin to the baby's hemoglobin. Just my thoughts but maybe I am wrong.
 

that70sfan11

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The main point here is that when you bleed, you bleed crimson

therefore, everyone is a SOONER! BOOMER SOONER!!!! :D







^^:troll:
 

HopefulAg

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Meh, I bleed maroon, which means I'm one step away from full blown cyanosis according to this thread.
 

heylodeb

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Husband and I are almost in tears from reading all these posts today. Laughter started with the pissy pre-med post in the internationol trip thread and continued when I moved over here to the color of blood.

Too bad we'll all be back to becoming stressful crazies in a couple months.:love: