Fig. 3

Fig. 3

The wetting model for epiboly. (a) At the onset of epiboly, the embryo consists of the cell cluster at the animal pole of the embryo (gray) and the yolk at the vegetal pole (yellow). The cells at the cells-medium and the yolk-cells interface interact mechanically with adjacent cells, resulting in net forces of ${\gamma }_{\text{c}}\left(t\right)$ and ${\gamma }_{\text{yc}}\left(t\right)$, respectively. The mechanical interaction of the cells of the precursor film leads to the contribution ${\mathit{}}_{\text{y}}c\left(t\right)$ to ${\gamma }_{\text{y}}\left(t\right)$. In addition, the actomyosin ring exerts a pulling force