Modern Mythology

The blood in a normal, living human being’s veins is:

A) Red

B) Blue

C) Green

D) Other (please specify in comments)

Extra credit if you know whether “being exposed to air” matters.  Triple extra credit if you can discuss the usual difference in color between arterial and venous blood.

(This post prompted by a discussion at work a few weeks ago, in which a patient insisted that I was wrong on this question, and that she was right.  I dropped the discussion, but oy.)

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6 Comments on “Modern Mythology”

  1. tina Says:

    Um… it’s blue until exposed to oxygen. Then it turns red.

    Arterial and venous gets me. One goes from the heart and carries O2. The other is to the heart and to be oxygenated?

    I nearly failed biology… can you tell?

  2. Care Says:

    Oooh, I know this one! Good grief – what is it with patients who think they are smarter than the average bear. Bleh.

  3. bri Says:

    I also think it’s blue until exposed to oxygen and then red. Is that correct or a myth?

  4. StillTrying Says:

    Believe it or not, human blood is always red. The blue thing is a myth that sucks in a lot of people.

    Check with a local hemetologist or lab, or you can google a reputable source.

  5. Jean Says:

    Blood in the systemic arteries (traveling from the heart to the oxygen-using cells of the body) is red-colored, while blood in the systemic veins (traveling from the oxygen-using cells back to the heart) is blue-colored. With a spectroscope these changes are very obvious. Here is the best explanation as to why: We know that the shape of the heme group and the hemoglobin protein change, depending on whether hemoglobin is oxygenated or deoxygenated. The two conformations must have different light-absorbing properties. The oxygenated conformation of hemoglobin must absorb light in the blue-green range, and reflect red light, to account for the red appearance of oxygenated blood. The deoxygenated conformation of hemoglobin must absorb light in the orange range, and reflect blue light, to account for the bluish appearance of deoxygenated blood.

    As for green blood this occurs when a patient suffers from Sulfhemoglobinaemia. This causes the blood to take on a green color, and can be fixed just by discontinuing the use of the sulfur based products.

  6. elowyn Says:

    It’s always red, but different shades of red – you can draw venous blood in a vacuum container (so no appreciable air) and it will be red. But the reds are different (bright scarlet for arterial, deep cherry-purply red for venous.) So a bluish tint, but not blue. And I have a feeling that when most people are saying “blue” they’re thinking “the color of a smurf” or similar, not “almost maroon”. Just a hunch.

    Snopes has a good article on this one, IIRC. 🙂 Thanks for playing!


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