In essence all blood vessels consists of a tube with the luminal lining of and endothelial cells surrounded by varying amounts of smooth muscle cells and extracellular matrix. however the structure of each of these components varies in different parts of the vasculature .
According to functional needs to accommodate pulsatile flow. And higher blood pressures arterial was are thicker than veins and invested with reinforcing layers of smooth muscle cells. As arteries narrow to the ratio was thickness to lumen diameter increases to allow more precise regulation of intravascular pressures veins. On the other hand are dispensable involve vessels with high capacitance in keeping with the specialisations certain. Pathologic lesions characteristically involve a particular kind of vessels. for example atherosclerosis occurs mainly in larger muscular atrophies .Why hypertension effect small arterials and specific forms of vasculities. Selectively involve vessels of only a certain calibre vessel walls are organise into three concentric layers intima-media and adventitia.
These layers are present in all vessels. But are most of their and in larger vessels and particularly arteries. The intima consists of an endothelial cell. Monolayer on a basement membrane with minimal underlying ECM, surrounded by loose connective tissue.
Nerve fibres and smaller vessels of the advantage. And external elastic lamina is present in some arteries . Defines the transition between media and advantage of diffusion of Oxygen and nutrients from the lumen in adequate. To sustain thin-walled vessels , and the intimo smooth muscle cells of all vessels in large and medium sized vessel. However small 8 Furious within the adventitia supplied the outer half to two thirds of the media.