Fig. 5.

Our model predicts a thin boundary layer close to the cortex. (A) A zoom of the region close to the cortex, meant to highlight that substantial cytoplasmic flows are observed relatively close to the cortex, as observed in experiments. In fact, the no-slip boundary condition forces the sol velocity to drop to zero at the cortex, but the decrease is sharp and happens in a boundary layer that is micron-thick. This is visually demonstrated by taking the velocity in the box shown in panel (B) and plotting its amplitude vs the position (normalized by the width of the embryo at that AP position). Panel (C) shows results for our simulations, and panel (D) for an analogous region in the experiments. The segmented vertical lines represent the point from which no experimental velocities can be resolved, which reinforces the impossibility of resolving a boundary layer such as the one present in the simulations with the available experimental data.