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View Full Version : What is the true color of blood?


diggleblop
09-20-2006, 03:29 PM
I've heard so many different things. It's blue, it's greenish, it's dark purple. What's the true color before it hits oxygen? Even google has conflicting answers.

Colibri
09-20-2006, 03:54 PM
Venous, deoxgenated blood is dark red. This is easily observable if you have a blood sample taken with a clear syringe. (Although there is air in the syringe, it's not enough to oxygenate the whole sample.) Certainly not blue or green.

Colibri
09-20-2006, 03:58 PM
I should clarify, there should be almost no air in the syringe if blood is being drawn, rather than just very little.

cainxinth
09-20-2006, 04:00 PM
I asked my father the cardiologist when I was ten. He said it was blue.

AncientHumanoid
09-20-2006, 04:00 PM
A duck!

Colibri
09-20-2006, 04:02 PM
I asked my father the cardiologist when I was ten. He said it was blue.

He must have been joking, or taking about lobster blood.

633squadron
09-20-2006, 04:11 PM
I've heard so many different things. It's blue, it's greenish, it's dark purple. What's the true color before it hits oxygen? Even google has conflicting answers.

Uh, blood often contains oxygen, so this really doesn't make sense. What you probably mean is "What's its true color while it's in blood vessels?"

The answer is basically "It depends".

Blood with a high oxygen content is bright red. This is the blood you'd find in your arteries, which take oxygenated blood to your tissues. You will find that blood from your capillaries is fairly well oxygenated, so it is a fairly bright red. Thus, a superficial cut will issue red blood.

Blood with a low oxygen content is a dark red/maroon/purple. This is the blood you'd find in your veins, which take deoxygenated blood back to your lungs. This is the color of blood you see when someone takes blood for tests; it's also the color you see when you give blood.

The color difference comes from the electronic state of the "heme" complex that is the core of hemoglobin, the protein that binds oxygen.

Red blood cells contain hemoglobin; dissolved O2 and N2 migrate through the alveoli in your lungs into the lung capillaries where the hemoglobin binds the O2. Hemoglobin holds onto the O2 until it reaches cells. At that point, other proteins release the O2.

One of the reason carbon monoxide poisons you is that hemoglobin binds CO better than O2. CO eventually takes over all the hemoglobin, so your body is unable to uptake O2.

When hemoglobin binds O2, the absorption spectrum of the heme "relaxes" so that it reflects a lower wavelength of light (bright red). When the O2 is released, the heme reconfigures and absorbs/reflects a higher wavelength (blue/purple).

thelurkinghorror
09-20-2006, 04:25 PM
The pertinent mailbag article: https://academicpursuits.us/mailbag/mbloodrd.html

Mangetout
09-20-2006, 05:21 PM
But what colour is it when nobody is looking? In a forest.

picunurse
09-21-2006, 07:38 AM
Blood always has oxygen in it. Arterial blood has (ideally) more oxygen than venous blood, but there is still some. Blood is red, bright or dark, but red, nevertheless. Of course, once outside the body for several days, it appears black, but adding water shows it as red. Here is a simple answer to: "Why is blood red?" (http://newton.dep.anl.gov/askasci/bio99/bio99423.htm)

Mangetout
09-21-2006, 07:55 AM
Just to note the the OP didn't specify human blood.

Earl Snake-Hips Tucker
09-21-2006, 09:26 AM
Blood with a low oxygen content is a dark red/maroon/purple. . . When the O2 is released, the heme reconfigures and absorbs/reflects a higher wavelength (blue/purple).

Purple? Human blood is sometimes purple?

Blue has a higher wavelength? Don't you mean frequency?

Ludovic
09-21-2006, 09:32 AM
A duck!No! Red! ahhhhhhh!

Cervaise
09-21-2006, 10:46 AM
But what colour is it when nobody is looking? In a forest.What if the blood is on a treadmill?

Nava
09-21-2006, 11:21 AM
I've heard so many different things. It's blue, it's greenish, it's dark purple. What's the true color before it hits oxygen? Even google has conflicting answers.

You realize that about half the blood in the body has "hit oxygen" in the lungs, right?

So that half is red. Blood-red, more specifically ;)

chowder
09-21-2006, 11:32 AM
So why are my veins blue?

AncientHumanoid
09-21-2006, 12:18 PM
So why are my veins blue?


Royalty?

Ludovic
09-21-2006, 12:21 PM
What if the blood is on a treadmill?Blood on a treadmill won't echo, and no one knows why.

Colibri
09-21-2006, 03:23 PM
So why are my veins blue?

Read the link in post #8.

Elendil's Heir
09-25-2006, 03:37 PM
When I was a Civil War reenactor, I bled Union blue, baby.

bbs2k
10-05-2006, 09:58 AM
Mods, please forgive the resurrection of a zombie thread, especially one started by, well.. nm, but I really wanted to contribute.

Since a lot of talk has been related to phlebotomy and drawing blood into tube, I wanted to relay a color story. Blood in a specimen tube, once centrifuged, is generally separated into three parts. The actual red blood cells (which make the blood red colored whether it's arterial or venous), the buffy coat (a thin layer of white blood cells and platelets), and the plasma/serum (the liquid part of the blood that is used for transportation of the blood cells, blood protein, etc...).

Although the blood is always red in different shades, there are certain types of medications that can make the plasma/serum a variety of colors. This is in my experience, I'm not gonna dig up a bunch of cites (sorry, bad etiquette once again). These colors can range from green to even a purple. The purple patient sent me running to a PDR to try and find out what med the patient was on to cause this. I couldn't actually find the source, but trust me, the plasma was purple!

And there's always the issue of lipemia (http://en.wikipedia.org/wiki/Lipemia) and hemolysis (http://en.wikipedia.org/wiki/Hemolysis). The latter caused by internal blood cells lysing or a bad needlestick draw, the former caused by eating too many cheeseburgers before a blood draw. So please, skip the McDonalds visits before donating blood. Thank you for donating, but you are actually passing on the cholesterol!

bbs2k
10-05-2006, 10:02 AM
[ quietly sneaks back into the room]

Oh yeah, sorry, I should just FYI for anyone who doesn't know. The normal color of plasma/serum is a yellow/straw color. You probably already knew this, and I should take my exit quickly...

chowder
10-05-2006, 12:27 PM
As a Manchester City fan I can assure you my blood is blue.

Red!!?? :eek:

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