The origin of hematopoietic stem cells in the ontogenesis of vertebrates

A review of the origin of stem blood cells in ontogeny of vertebrates is presented. The comparative analysis of the data on laying, determination and migration of the hemopoietic precursor cells during embryogenesis in various taxonomic groups (teleosteans, urodeleans, anurans, avians and mammals) is performed. The change of the hemopoietic site and erythroid cells populations has been described. The data on sources of blood cell precursors and the origin of hemopoietic cells in the primordiums of hemopoietic organs were classified. A conclusion has been reached that in the course of evolution the hemopoietic anlage is gradually divided into two parts: one part migrates to the extraembryonic (ventral) mesoderm and another one remains intraembryonically and gives rice to the predecessors of definitive hemopoietic stem cells.