How to build a person! – 3: Breathe!

So far in Science Burrito’s epic quest to build a person with nuts and bolts, we have made a skeleton and covered it in blood. This is pretty grim, especially so far from Halloween. Maybe it’s time for a breath of fresh air… That’s a pun, by the way, and I will not apologise for it!

There are two main things blood move around. Food, and oxygen. We’ll come back to food at a later date. For now, let’s look at oxygen.

Oxygen is in the air. It’s what we take out of the air when we breathe in, and we do that so that we can generate the energy our bodies need from it. This also requires food again, so you can see how intricately the two are linked. How do we turn this oxygen into energy? Well, basically, we light fires in our cells!


Ok, that’s a bit of an exaggeration. But, if you take a lump of sugar, and set fire to it (do NOT take a lump of sugar and set fire to it) the energy is released from the sugar to produce heat in exactly the same way as our cells make energy: by oxidation! That means the sugar is combined with oxygen and energy is released. Our cells are not actually on fire, because they release that energy in a very controlled way. But it is the same kind of energy released in the same kind of way.

We get that oxygen to the cells, via the blood stream, and we get it into the bloodstream via the lungs.


Here’s the easy bit, because we’ve covered some of this before. The lungs are like a big diaphragm pump. The diaphragm expands and the lungs fill with oxygen like an inflating balloon. The diaphragm contracts and we breathe out. When we get hiccups, that’s the diaphragm jumping when it shouldn’t.


We said previously though, that diaphragm pumps can be tough for us to make and tend to have to be big, and come with a lot of extra equipment and are hard to carry around. Last time, we replaced the heart with a simple centrifugal pump, and there’s nothing to stop us doing that again. We can have one pump for in, and one for out. We can make them pretty small, again like we said before, and so they fit inside our giant body pretty well.


Now we have a mechanism for filling the lungs, what shall we make them out of? Well, they only need to be permeable (leaky) to gases like oxygen and carbon dioxide. It’s actually pretty easy to find materials that aren’t air tight. Probably more things are not air tight than are. In fact many things rely on their being oxygen permeable. Contact lenses for instance need to allow oxygen to get to the eye. Something complicated sounding like polymethylpentene (PMP) will do us. It’s strong, heat resistant and very, very oxygen permeable. We wrap the blood capillaries we made last time around our PMP lungs and away we go.

Lungs. Done. Easy.



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