We don’t usually think about our cells moving, at least not of their own accord. WE move, not our cells, right? My leg moves because I tell it to, and my diaphragm contracts, drawing air into my lungs, because my brainstem tells it to—it doesn’t just contract on its own.
But some of our cells DO move. I’m talking, here, (I’ll bet you guessed it) about neurons.
In very early development, a process called delamination occurs. Neuroblasts—cells that will differentiate into neurons or glia—grow bigger than the surrounding cells and kind of squeeze out of epithelium.
Okay, see? The big circle made of little boxes (cells) with dots (nuclei) in them is a grastrula stage embryo. The pink cells are about to delaminate, and the red, round cells already have. It occurs in several waves, which is why the bottom diagram of the embryo shows both cells that are going to delaminate and cells that already have. (Aren’t pictures great?)
There’s more of this freaky cell moving crap going on in the cortical tissue in the brain. The cortex develops in layers. New cells are “born” through cell division in the most interior layer (the ventricular zone), and they migrate up toward the surface layers. The younger cells get to kind of crawl up these older cells, the radial glia, to reach the upper layers. Cool right? Yep, it’s picture time again:
….And I guess that’s all for now because I still have about 10 pages of that really long chapter to read before class tomorrow morning.