Is blood blue? Only if it’s not real blood

27 06 2008

In keeping with the Myers-free zone theme… (let’s see how long I can last‡)

I just had to read Greg Laden’s post when I saw the question: “Is Blood Ever Blue? Science Teachers Want to Know!“. I realised I knew the answer already after I’d read it*. (But I bet I didn’t convince you with that either).

This is cool science, and definitely does point out a difficulty in how some people obviously take stuff at face value when you present it to them. Metaphors can be confusing to your audience if they don’t recognise it as a metaphor. But I think a few more people might remain confused if those respiratory/circulatory diagrams were mere shades of red. Blue is a good colour to associate with it, as veins are blue the way we see them. But does this mean if our

In the comments you can find a reasonable explanation as to why blood looks blue in your veins. I’m currently visiting someone else’s house and don’t feel comfortable borrowing milk and red marker. Even in the name of science. See, some biomedical scientists have ethics.

Another thing I’m going to point out in response to the comments is that invertebrates, like crabs and most molluscs, don’t have blood. They have a blood analogue haemolymph, a internal fluid that combines properties mammalians of blood, lymph and interstital fluid (in a less the anthropocentric world, the opposite is the real truth, these three fluids are actually derived forms of haemolymph, I digress). The reason why this is blue is because they rely on a copper oxygen transport system (haemocyanin), in stead of our iron based one (haemoglobin). As the Iron Age is superior to Copper-based technology, mammalian supremacy is once again proved correct (thank you Sid Meier).

‡Yes, I know, technically I did link to he-who-shall-not-be-named in the last post

*Another commenter, Sven DiMilo, brings up the reason why I “knew” the answer before reading. Take note when you blood/have a test. Venous blood is taken into a vacuum, does it look blue to you?




One response

11 08 2008
How a solar sail works « It’s Alive!!

[…] really enjoy these sort of posts, such as Greg’s “Is blood blue?”. Slake my thirst for […]

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