Anatomy and pharmacology of vessels

A typical blood vessel is arranged in three distinct layers forming concentric circles. The innermost layer in contact with the blood is composed of endothelial cells on a basement membrane through which the endothelial cells and underlying vascular smooth muscle cells of the medial layer can communicate. The endothelium releases mediators and factors that have effects on vessel diameter, platelet adhesion and thrombus formation and inflammatory cell adhesion. The thickness and elasticity of the medial smooth muscle layer is dependent on the position of the vessel within the vascular tree and is adapted to the function of the vessel. The adventitia contains neural varicosities that modulate vessel diameter, and recent work has highlighted a paracrine role of the adipose tissue surrounding blood vessels. The adventitia also contains fibroblasts and inflammatory cells, such as resident macrophages. This chapter discusses blood vessel structure and function with a particular focus on how physiological mediators alter vessel diameter and how this function can go awry in some common cardiovascular diseases