That isn't the question (in a prior job I studied the physiology of the nail unit). Most cells don't normally have an orientation, so you'd think that thefollicle would push out a hair in some random direction, sometimes towards the outside world and sometimes in the direction of your bones.
Obviously they don't (!) but the question is how?
The nail is the same: the lunula emits these keratinocytes in only one direction; even more weirdly it's a planar structure.
> Obviously they don't (!) but the question is how?
Don't cells "just" orient themselves using mechanotransduction [1] or am I missing something? That's a bit hand wavey but since cells don't form 3d structures in tissue themselves, they orient against the extracellular matrix using mechanotransduction and other growth factors.
The development of multicellular life was essentially cells learning how to orient themselves into a digestive tract.
Obviously they don't (!) but the question is how?
The nail is the same: the lunula emits these keratinocytes in only one direction; even more weirdly it's a planar structure.