In ruminants, the elongation of the conceptus is marked by an anisotropic growth of the extra- embryonic tissues prior to implantation. This has not been related so far to processes such as cell deformation or specific cell organisation and could result from oriented cell divisions within the trophoblast [Wang, CRAS, 2009]. However, since the endoderm cells that underline the trophoblast display highly anisotropic features [Flechon, Genesis, 2007] it could be that this extra-embryonic layer drives the elongation process. To test these 2 hypotheses: oriented trophoblast division and endoderm driven process, we have started analysing these cells, their divisions and their interactions to extract biological and/or biophysical parameters. Once evaluated, we could integrate them and aim at the modelling of this ruminant specific morphogenesis.