Figure 1.
The vascular plexus, mechanisms of angiogenesis and the remodeled vasculature. The vascular/capillary plexus, composed of an interwoven capillary network with intervening avascular spaces, and in which the presumptive arterial (red) and venous (blue) sides have been specified, is primarily generated by vasculogenesis. Various mechanisms of angiogenesis – fusion, intussusception, sprouting, and regression – contribute to changes in vessel diameter and vessel density. Remodeling of the plexus results in the formation of a hierarchical vasculature tree with large diameter arteries and veins that are connected to progressively smaller diameter/distal capillaries. Simultaneously, vessels become stabilized by the recruitment of mural cells (pericytes and smooth muscle cells) (tan).