The previous post in this series can be found here.
Over the course of my 'human machine' series of posts I've tried to convey the intricacy and beauty of our biological engineering, and demonstrate that we are incredibly well-engineered machines whose complexity and originality go all the way down to the atomic level. In this week's post, I will be exemplifying this with one of the best cases that I can think of; how we transport oxygen around our bodies. I feel that this is a great story to tell because it is one that most people might think that they know well, but that actually is far more complex and subtle than it may appear, and that demonstrates how our lives are highly dependent on perfectly evolved processes working on the subatomic scale.
"It will have blood, they say."
I'm sure that anyone reading this blog is fully aware that we need oxygen to survive (although if you want a more detail explanation of exactly why then I direct your attention to a previous post of mine available here), and anyone remembering their primary school biology will know that oxygen is transported around the body by the circulatory system, i.e. the blood. Most of the cells within your blood are the famous red blood cells (to distinguish them from the immune cells - the white blood cells), which are, unsurprisingly, responsible for blood's distinctive colour - earning them the respect of horror movie aficionados everywhere. You have roughly 20-30 trillion red blood cells in you as you read this, each of which is about 7 microns (i.e. 7 millionths of a metre) in diameter. They shoot around your body, taking roughly 20 seconds to make one circulation, and have just one job; take oxygen from the lungs (where there's lots of it) to the tissues (where there's not). So specific are they to this job that they don't even bother having a nucleus, thereby removing all possibility of them doing anything else.
|Human red blood cells - you make 2 million every second!|