Mathematical models of mass transfer in the vascular walls
As illustrated in detail in chapters 1 and 2, the arterial wall is a heterogeneous structure consisting of several layers which strongly differ in their thickness and in their biological and physical properties, that we briefly recall here for the sake of clarity. The layers constituting the wall are the endothelium, the intima, the internal elastic lamina or lamella (IEL), the media and the adventitia, see Fig. 7.1 for a simplified sketch. The endothelium is a type of epithelium composed of a single layer of smooth, thin cells that lines the heart, blood vessels, lymphatics, and serous cavities. It forms a continuous lining on blood contacting surfaces in the vascular system, providing the principal barrier against the entry of cholesterol and blood cells into the wall and inhibiting platelet adherence to the vessel walls. Endothelial cells create chemicals and control the transport of mass into and out of the wall. The sub-endothelial layer is an extra-cellular matrix of randomly distributed fibres, mainly collagenous bundles and proteoglycans (glycoproteins which have a very high polysaccharide content). This layer is surrounded by the IEL, which is composed by elastic fibres. Under normal physiological loading, the fibres form an approximately circular band. Together with the sub-endothelial layer it helps the wall to withstand haemodynamic stresses. Outside the IEL there is the media, which is made of smooth muscle cells and is the primary regulator of vessel diameter. The outer layer is the adventitia, which is a complex structure that merges into the surrounding tissue.
KeywordsArterial Wall Wall Layer Fractional Void Volume Internal Elastic Lamina Electrical Analogy
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