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

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

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

4. 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

5. 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

6. 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