Arterial wall


Arteries have three concentric layers of tissue:

the intima the media the adventitia

The internal elastic membrane borders the intima and the external elastic membrane separates the media from the adventitia.

The intima surrounds the lumen of all blood vessels and is a single continuous layer of endothelial cells.

The endothelial cells synthesise regulators of thrombosis including prostacyclin, plasminogen activator and heparin like molecules.

Endothelial cells produce prothrombotic molecules including Von Willebrand factor, and plasminogen activator inhibitor.

The intima modulates blood flow and vascular reactivity through synthesis of vasoconstrictors:


angiotensin-converting enzyme

Intima synthesizes vasodilators

nitric oxide


Intima regulates immune and inflammatory reactions, elaborates interleukins, adhesion molecules and histocompatibility antigens

The Media’s smooth muscle cells dilate and constrict to accommodate blood flow

The Intima is perfused by small arterioles called vasa vasorum

Adventitia is the outer layer of the artery made up of connective tissue, perfused by vasa vasorum.

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