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Humans (and all animals, really) are pretty complex. We are made of many different organs, types of muscles, bones, and a whole host of other things, all of which need to work together in order to function properly.
When you look closely enough, all of those different parts and pieces are made up of cells. The cells all perform different functions depending on the type of cell they are. For example, a cell in the brain is going to be different than a cell in the liver.
That begs the question, how do the cells know what they are supposed to be doing and where they are? This is an even bigger question while we are developing and all our various parts need to form from cells that haven’t yet been specialized.
Even as adults, it is a very difficult concept to understand. If, for example, you get a cut on your arm, cells are sent to that area to repair the skin, but how do they know to become skin? Obviously your body doesn’t have a storage tank with extra cells of every type ready to be deployed.
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The answer is that the body can make any type of cell that is needed, and even cells that can become any type of cell as demand arises. To get where it needs to be and become what it needs to become, the body uses something called morphogens.
The DNA of a cell is programmed to respond in specific ways based on when there is an abundance of morphogens and where the density of morphogens is higher or lower. A crude analogy is that the morphogens work like a trail of breadcrumbs for the cells to follow.
When the liver needs some extra cells to repair itself, for example, it will trigger the morphogens to react in a way that ‘calls’ for the cells that are needed.
The morphogens throughout the body are regularly being created and destroyed with the goal of remaining evenly distributed throughout. If that distribution is off, that generally means that new cells are needed in a given area. The body does have some checks and balances to make sure that even if the level of morphogens are uneven, cells won’t just create new tissue where it isn’t needed, but that is a whole other complex topic.
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The concept of morphogens was first predicted by Alan Turing who coined the term in the 1950s. They weren’t actually identified until 1980 when Christine Nusslein-Volhard found them in fruit flies, winning her a Nobel Prize for Medicine.
So, as you might expect, cells are able to tell where they are in the body and what type of cell they should be is extremely complex. Fortunately, it also works quite well.
If you think that’s impressive, check out this story about a “goldmine” of lithium that was found in the U.S. that could completely change the EV battery game.