How to build a person! – 1: Bone!

Before we start! Sorry about the broken GIFs. I shall upload fixed versions soon!

If you came to this blog post hoping to see something for adults… then you’re in luck, because science is for everybody. If you came to this blog post hoping to see something only for adults, then you’re out of luck, because science is for everybody.

Mankind has created some incredible things. The Large Hadron Collider, the Hoover Dam, the Great Pyramids. Still though, one of the most amazing thing that people make is more people. Now, I promised at the start to give you an honest view of science, with no exaggeration. So, here is the truth. Making new people is something people do every day. It’s no great miracle, we probably make too many of them, and honestly, we have very little to do with it. Nature does most of the really hard work. But, that’s kind of my point here. The human body is an incredible machine, which is constructed pretty much automatically by nature within us, all we need to do is supply the machines within us the fuel they need to succeed.

O.K. I admit at this point that we also need to carry them and give birth and then raise them, and that’s all pretty tough stuff, but what I want to talk about hear is the biological human machine: the cells and tissues and organs that go to make a person. I want to ask the question, if we wanted to make a person, from the bottom up, with tools and hands, rather than letting nature do it all, what would it take? I’m hoping, once a month, to publish a post exploring a different part of the body and how we might try to replicate it with current technology. To begin with, let’s strip everything right down to the bare bones…

The first thing you need in any project is a good foundation to build on, and the body is built on the bones.

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So, bones are easy right? You just need something strong. Metal is pretty tough, so how about iron? Here’s what it would look like if your bones were made of iron.

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That’s you on the floor there. Get up, go on. You can’t! That’s because iron is really heavy. Ok, so no problem, there are lighter metals. Why don’t we use aluminium?

Ok, great, you can stand. Pick up that mildly heavy box will you?

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Ooops. So, aluminium is light but it’s pretty easy to bend. So we need something that is light and strong. Let’s examine this a bit more closely.

There are lots of different types of strength. Some things are very strong against compression: you can push on them really hard and they don’t get smaller or break, like metal. Other things break very easily, leg an egg, or are easy to squeeze smaller, like cork. Bone is very good at this one.

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Some things are very strong against tension: you can pull on them really hard and they don’t get larger or snap. Again, metals are good example of this. Chalk is very bad example. Bone is pretty good at this one.

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Some things are very strong against shearing: they are difficult to cut. Diamond springs instantly to mind as strong, the so-called “hardest substance”, but it is hella expensive. Something like paper is particularly weak, because as we all know, scissors cut paper. Bone is worst at this one. It is shear forces that usually cause breaks.

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But there is something bone has that metals don’t: Elasticity! Your bones can compress and stretch and shake and bend, and they pop back to where they started, as if nothing happened. Metals on the other hand, tend to stay in the shape that we force them into.

Ok, so we need something light weight, with good tensile, compressive and shear strength (better than bone if we can) but which is also very elastic, or before long our bones won’t fit in our body anymore. Is there anything like that?

Not really, no. This is where nature defeats us really. Making something as elastic as human bone is very difficult. The best we can probably find is, pretty amazingly, Kevlar!

Actually, this is not very surprising. Bulletproof vests need to be strong to compression and shear and need to be fairly elastic because that helps to absorb all the energy of a gunshot. So it isn’t surprising that it would make a decent bone material. It’s around the same density as bone too, so your bones wouldn’t be too heavy.

Excellent, so now we have bulletproof bones. That’s it right? We’re done! Nope. I’m afraid it is never that simple in biology. Nothing is allowed to do only one job because nature is always trying to be as efficient as possible. So, other than hold us up and keep us that way, what is it that bones do?

Well, have you ever wondered where blood comes from? We’ve all bled now and again, and we don’t worry about running out of blood (unless something is seriously amiss, then, if you’re not already in hospital, you need to be), so where do we make all our new blood? Ever heard of bone marrow? That’s where! In the middle of all this strong and elastic stuff is bone marrow, our own super protected, highly mobile, blood factories.

Can we do this artificially? Well it turns out we can. Or we believe we can, and we’ll know very soon whether we’re right or not when artificial job is trialled this and next year. And we’ve done it in the exact same way that bones do, by taking those magical things known as stem cells, which are basically blank slates can be turned into anything, and encouraging them to turn into blood cells. Alternatively, if we want to avoid any natural intervention at all, there are artificial alternatives, chemicals we can manufacture that do the same job as blood, namely carry and release oxygen. The only problem then is miniaturising the process. And because Kevlar is a weave, we can thread blood vessels through it to get the raw materials inside the bones and freshly made blood out of the bones and into the body.

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The last thing bones do, something the entire body does, so this is going to come up again and again, is heal. Honestly, this will be the biggest challenge we face when building our new person from scratch, but at least for simply patching a hole in a material, which is all we really need for a broken bone, we have a solution. Some very clever people have created a system of tiny tiny tiny tubes filled with two different liquids. When the tubes break, the fluids mix together and react. Just like a glow stick glows when you break it, these liquids become a tough solid, patching the broken area.

Brilliant! So, we have our first body parts, bones, made out of Kevlar. They’re even producing the blood we need to keep the rest of the body going. But how do we get that blood to where it needs to go? Cue, the circulatory system!


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