Tunica Externa Outermost layer of the blood vessel Composed of loose connective tissue

Tunica media Middle layer of the blood vessel Consist primarily of circumferentially arranged layers of smooth muscle

Tunica intima Innermost layer of the blood vessel Single layer of endothelial cells

Endothelial Cells Maintenance of a selective permeability barrier Regulation of thrombosis Modulation of blood flow and vascular reactivity Regulation of cell growth, particularly smooth muscle cells Regulation of inflammatory/immune responses Maintenance of extracellular matrix Involvement in lipoprotein metabolism

Endothelial Dysfunction Cytokines, bacterial, and viral products causing inflammation Hemodynamic stresses and lipid products (Lends to pathologic process of atherosclerosis) Hypoxia Influence the reactivity of smooth muscle cells both relaxing and contracting factors Produce other cytokines, growth factors, procoangulant or anticoagulant substances

Vascular Smooth Muscle Cells Control dialation and vasoconstriction of blood vessels Control elaborate growth factors Synthesize collagen, elastin, and other components of vascular repair Function lends to the normal vascular repair Lends to pathologic process of atherosclerosis