The human hand
Being Greek, I move my hands around a lot when I talk. I also drink a lot of tea (to blend in with my current surroundings…) We humans use our hands both to manipulate objects (to eat, work, play), and to express ourselves. In my case, trying to do both at once often results in spilled tea.
(As I was writing this, I thought: maybe as part of our exhibit, we should ask visitors to write down their favourite thing to do with their hands. But what if some of the …playful ones choose rude gestures? And what if they choose gestures I don’t even know are rude, because they are from a different part of the world?! Then of course I had to google “rude hand gestures of the world” and spend the next half an hour marvelling at how easy it is to inadvertently offend people. We have the “moutza” in Greece in case you’re wondering. But I digress.)
Here’s a very interesting fact about hands: most of the muscles that we use for hand movements are located in the forearm, instead of the hand itself. As you can easily tell if you touch them, our fingers are mostly bone, attached to the muscles in the forearm via cords of tissue called tendons.
The result of this strange arrangement is that our fingers are light, but very strong. Another useful result is directly related to our project. Since most of the hand muscles are located in the forearm, loss of the hand does not mean loss of all muscles. So if a person thinks about moving their hand, even if they no longer have it, they will still contract their hand muscles located in the forearm. We can use these contractions to control a prosthetic hand.
But what about the thumb? I hear someone ask. The thumb is different: most of the muscles that control its movements are located in the palm of the hand. Its movements are also more complicated, so it is generally a bit of a headache for prosthesis control and it deserves its own r̶a̶n̶t̶ post.
Not next time though. It is almost the end of January (already!), so it is time to have a look at how our exhibit preparation is going.
