shernren
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- Feb 17, 2005
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A follow up on blue blood:
We had a blood donation drive in my college yesterday, and I asked my group of A-Levels students (average age 18) "what color is deoxygenated blood?" I mentioned neither red nor blue in my question. Mind you, this is a physics class I'm teaching, and many of these students do not even take A-Levels biology, but most of them took biology in school.
The closest anyone got to blue was a lone voice saying "purple", but immediately a chorus of voices said either "deep red" or "brown". I then asked, "Have you ever heard of the idea that deoxygenated blood is blue?" They were stumped, but some of the normally more vocal kids said after a few seconds "Well, that's how the books draw veins - but blood isn't actually that color!"
Then I asked them how they know, and they said, "Well, it's that color when you bleed." I asked them how they knew the blood being bled was deoxygenated, and that's where they were stumped (it's because arterial bleeding is often fatal due to the higher pressure, so most bleeding comes from veins where the blood is deoxygenated). I gave them the final link, and then a lecture on how scientists are still trying to better understand the color of veins under the skin, and how that demonstrates how financial interests often drive research priorities. That's a rant for another day.
But the fact that they got so far was impressive to me, especially since this is not a fact officially taught in the high school system (namely that bleeding shows you the color of deoxygenated blood).
How is it that a group of Malaysian teenagers can intuitively arrive at a conclusion which a group of American adults require the authority of a blood technician to accept? There are many possible answers, most of which are not polite to describe here - so I shan't. But it is highly unlikely that it is because the scientific community genuinely thought blood was blue for any significant period of time in the last thousand years.
We had a blood donation drive in my college yesterday, and I asked my group of A-Levels students (average age 18) "what color is deoxygenated blood?" I mentioned neither red nor blue in my question. Mind you, this is a physics class I'm teaching, and many of these students do not even take A-Levels biology, but most of them took biology in school.
The closest anyone got to blue was a lone voice saying "purple", but immediately a chorus of voices said either "deep red" or "brown". I then asked, "Have you ever heard of the idea that deoxygenated blood is blue?" They were stumped, but some of the normally more vocal kids said after a few seconds "Well, that's how the books draw veins - but blood isn't actually that color!"
Then I asked them how they know, and they said, "Well, it's that color when you bleed." I asked them how they knew the blood being bled was deoxygenated, and that's where they were stumped (it's because arterial bleeding is often fatal due to the higher pressure, so most bleeding comes from veins where the blood is deoxygenated). I gave them the final link, and then a lecture on how scientists are still trying to better understand the color of veins under the skin, and how that demonstrates how financial interests often drive research priorities. That's a rant for another day.
But the fact that they got so far was impressive to me, especially since this is not a fact officially taught in the high school system (namely that bleeding shows you the color of deoxygenated blood).
How is it that a group of Malaysian teenagers can intuitively arrive at a conclusion which a group of American adults require the authority of a blood technician to accept? There are many possible answers, most of which are not polite to describe here - so I shan't. But it is highly unlikely that it is because the scientific community genuinely thought blood was blue for any significant period of time in the last thousand years.
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