We know, that cancer cell can travel across an organism.
Is this ABSOLUTELY impossible for NORMAL cells?
For example, is it EXACTLY ZERO probability to find some bone cells inside liver or some skin cells inside brain?
In non-living things and with molecules this is called "diffusion". Any two contacting things will penetrate inside each other after hundreds and thousands years.
Is something similar happening in living thing?
May be very slow?
Was this phenomenon searched for?
Are there some protection mechanisms against appearing wrong tissue cells inside another tissues?
I understand that cells appear in their places during grow, but in mature state I think it is not impossible for cells to travel.
I know that there are many cells that travel by nature, like blood cells.
The question is namely about "static" cells, those ones we normally regard as non-travelling.
Also, I understand that there are some mechanisms, making cells to prefer their normal places when they divide and grow.
But the question is what about all these mechanisms failed? And how often it happens?
For example, I am 40 y.o. So, how many bone cells from my legs are currently in my brains? Zero? One? Million?