Which coronary anatomy is relevant to the understanding of coronary artery atherosclerosis?

Updated: Apr 09, 2021
  • Author: Sandy N Shah, DO, MBA, FACC, FACP, FACOI; Chief Editor: Yasmine S Ali, MD, MSCI, FACC, FACP  more...
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Answer

The healthy epicardial coronary artery consists of the following 3 layers:

  • Intima

  • Media

  • Adventitia

The intima is an inner monolayer of endothelial cells lining the lumen; it is bound on the outside by internal elastic lamina, a fenestrated sheet of elastin fibers. The thin subendothelial space in between contains thin elastin and collagen fibers along with a few smooth muscle cells (SMCs).

The media are bound on the outside by an external elastic lamina that separates them from the adventitia, which consists mainly of fibroblasts, SMCs, and a matrix containing collagen and proteoglycans.

The endothelium is the monolayered inner lining of the vascular system. It covers almost 700 m2 and weighs 1.5 kg.

The endothelium has various functions. It provides a nonthrombogenic surface via a surface covering of heparan sulfate and through the production of prostaglandin derivatives such as prostacyclin, which is a potent vasodilator and an inhibitor of platelet aggregation.

The endothelium secretes the most potent vasodilator, endothelium-derived relaxing factor (EDRF), a thiolated form of nitric oxide. EDRF formation by endothelium is critical in maintaining a balance between vasoconstriction and vasodilation in the process of arterial homeostasis. The endothelium also secretes agents that are effective in lysing fibrin clots. These agents include plasminogen and procoagulant materials, such as von Willebrand factor and type 1 plasminogen activator inhibitor. In addition, the endothelium secretes various cytokines and adhesion molecules, such as vascular cell adhesion molecule-1 and intercellular adhesion molecule-1, and numerous vasoactive agents, such as endothelin, A-II, serotonin, and platelet-derived growth factor, which may be important in vasoconstriction.

Endothelium, through the above mechanisms, regulates the following:

  • Vascular tone

  • Platelet activation

  • Monocyte adhesion and inflammation

  • Thrombus generation

  • Lipid metabolism

  • Cellular growth and vascular remodeling


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