Poiseuille flow! Clearly established with link and addition to Wikipedia (fr; damn, how dare they display IPs? Fleury thinks that’s illegal 😉 ). And without need to have a sandwich with a top Extra-cellular membrane (which probably don’t exist and would make a first point for a corrigendum to ask for EPMAG).
Great thing, I learned something new and is well established that the way Fleury see the cellular flow is analogous to a Poiseuille flow.
This is for a viscous liquid flowing against a surface with friction. Hmm, friction. Let’s say that the flow is from left to right. Where do you expect tensile stress? On the left, or on the right? Answer quickly, intuitively, without recourse to your course of physics.
Right! Tensile stress on the
What if there is a membrane under your viscous fluid traveling to the right? What will you expect on the right?
Now come on, VF considers the flow to be Poiseuille like and at the same time expect tensile stress at the front of it. Should I ask him his opinion?
Well, not this time. I got a few seconds free so I decided to go experimental. The most difficult part for the setup was to find an eraser. Rare stuff these days. But I did found one. Why an eraser? Because VF use it as an example in EPMAG. I didn’t use it the same way as he did, but I got an eraser. The rest of the necessary stuff include a piece of Saran wrap, some adhesive tape, less then a milliliter of water and a glass covered lab bench.
The bench was cleaned, a few drops of water was set on the clean surface (lubrication factor), covered with a piece of Saran wrap which was fixed on the bench with adhesive tape. The eraser was placed at the center of the setting.
Using the left hand I pushed the eraser from the left to the right, to simulate the flow. While with the right hand I was photographing the result. And here it is annotated, the arrow indicating the direction the eraser was pushed:
You intuition was correct.
Now, what if I pushed harder, so the tensile stress would be superior to the resistance of the wrap foil? One may expect a crack. A Saran crack in this particular case. A Saran crack with eraser. Left or right side?
Well, left side definitively.
Now, WTF has to do the Poiseuille Flow with the eventual crack of the basal lamina of the epiblast? Which would be at the right side if any crack existed. Well, probably nothing at all.
After dropping the top plate, it may be wise to drop the considerations about the Poiseuille flow. Who think differently and why?