Hydraulic forces tearing of intercellular contacts that help the germ cells to regroup and move on to the next stage of development.

After fertilization, the resulting embryo begins to divide into a ball of cells. But the ball of cells is just the beginning: if we take the embryo of mammals, we see, as in the embryo there is a cavity filled with fluid, and the cells are grouped on one of its poles (that’s not counting those that form the wall of the embryo). Subsequently, those cells that form the wall of the vesicle of the embryo (called the trophectoderm), help him to implant in the uterine wall and form the placenta.