Figure 1.

Development of embryonic vasculature begins in blood islands. Blood islands contain angioblasts at the periphery. Angioblasts differentiate to endothelial cells surrounding the primitive hematopoietic stem/progenitors. Hemogenic endothelium serves as an additional source of vascular cells, which differentiate into the hematopoietic lineage. To meet the needs of the growing embryo, blood islands coalesce to form the primitive vascular plexus, which undergoes rapid remodeling to establish a mature vascular network.