[Emergence of the endothelial network during embryonic development].

The avian model provides an experimental approach for dissecting the origin, migrations, and differentiation of cell lineages in early embryos. In this model, the endothelial network was shown to stem from both the somites and the splanchnopleural mesoderm. The somite line age produces only endothelial cells, whereas the splanchnopleural line age also produces hematopoietic stem cells. Potentialities of the mesoderm are determined by a positive influence from the endoderm and a negative influence from the ectoderm. A novel mode of blood-borne angiogenesis is also described.