ABSTRACT
How Does the Vascular System Develop and Growl T he vascular system is one o f the first organs to develop in the embryo. Cells o f the
m esoderm form blood islands, consisting o f endothelial progenitors (angioblasts) and haematopoietic cells. These islands fuse and angioblasts differentiate into a primitive vascular network o f endothelial tubes, a process known as vasculogenesis’1 (see Fig. 1). These tubes are sheathed by a basement membrane consisting of extracellular matrix (ECM) molecules such as laminin, collagen, nidogen/entactin and various proteoglycans.2
