A couple of weeks ago I got a splinter in my thumb. It was about 3mm long and big around as a sweing needle. It broke off clean at the skin level, but went in-between several layers of skin. There was no blood. Rather than pick at it, I cleaned the “wound” and kept a close eye on it.
As the days went by, I could see the outline of the splinter in my thumb. Some callous-like skin was forming around it, but it didn’t hurt, change color, or anything weird.
After about two weeks, the surface layer of skin began to peel. I removed the skin and could see the very end of the splinter. I grabbed a pair of tweezers and pulled the splinter out. It was no longer a recognizable piece of wood. It looked more like a piece of thread. I was able to remove the rest of the dead skin and reveal a small patch of new pink skin underneath. The spot is now almost completely healed. Another few days and you’d never know anything had happened.
Your body digested what it could then attempted to encyst it. That’s how the body deals with foreign objects.
Once the body knew it was there it began attack it. Various immune cells dumped digestive enzymes, peroxide and a host of other chemicals into the fluid around the splinter. As it broke up into smaller chunks these were engulfed by immune cells and seriously bombarded with digestive compounds. The result was much the same as if the splinter had been swallowed. Most of it got broken converted into gas or some substance that could be excreted.
The problem is that the body can’t digest cellulose, which is what makes up the ‘skeleton’ of plants. So that material remained behind although the simpler carbohydrates and proteins that gave the splinter form and colour were all removed. The end result was a thin piece of cellulose. Since the most common example of a thin piece of cellulose is a cotton thread it’s not really surprising that it looked like a piece of thread.
Since the cellulose couldn’t be digested by the body it set about quarantining it. It did that by building up a layer of thick walled cells with heaps of connective tissue, essentially an early form of cyst. If it was much deeper the cyst would have become a permanent hard lump that kept than undigestible material from the rest of the body. Since it was close to the surface that was able to be peel off the top layers and expose the indigetsible material for removal.