Cell movements in the egg cylinder stage mouse embryo.

Embryonic development does not simply consist of the growth of a preformed miniature foetus or homunculus. It is a tremendously dynamic process, characterised by a great deal of cell movement and tissue rearrangement. For example, during embryogenesis the forming heart starts ahead of the forming brain and only comes to lie in its more familiar position with respect to the brain following extensive tissue movements. This chapter looks at the movement of the anterior visceral endoderm, a signalling centre in the early embryo that is responsible for the correct orientation of the anterior-posterior axis. © 2012 Springer-Verlag Berlin Heidelberg