Angiogenesis is the natural biological process by which new blood vessels are formed. It is a normal process during the development of the fetus and the growth of the body from childhood to adulthood as the need for more blood supply arises. The development of new arterial branches and veins also happens during reparation and replacement of damaged tissue and during the formation of malignant tumor.
Angiogenesis also takes place in the cerebral cortex when new synaptic links are established among neurons during the process of learning new skills, be it intellectual or motor. When there is new synapses in the brain, new support cells, such as oligodendrocytes and astrocytes are formed and the need for more blood supply arises; these cells are the support cells of neuron axons.
Angiogenesis is caused by the development of vascular endothelial cells within a parenchymal tissue as a need to improve the supply of oxygen-rich blood to new areas which are the result of natural growth or development. For example, when an athlete develops muscles when he lifts weights, there is the need for more blood supply for more muscular mass. These squamous endothelial cells multiplication is due to the endothelial growth factor, which is a protein. Endothelial cells make up the single wall of capillaries and they also form the inner wall of arterioles and arteries (tunica intima). As endothelial cells divide, they in turn secrete more growth factor, which stimulate the growth of smooth muscle cells as well. Smooth muscle cells constitute the middle layer of artery wall.
Angiogenesis is very important in the recovery of heart muscle damage after a heart attack caused by coronary artery occlusion. Since the formation of new blood vessels creates important anastomosis (vascular connections/bridges) that prevent damage when an artery or arteriole get occluded or burst. Thus, it is an important biological tool to repair tissue but it also protects both the myocardium and the brain tissue from damage as anastomosis ensure permanent blood supply.