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The endothelium: A primer

Katherine A Hajjar, MD
William C Aird, MD
Section Editor
Lawrence LK Leung, MD
Deputy Editor
Jennifer S Tirnauer, MD


Endothelial cells (ECs) form the lining of all blood and lymphatic vessels within the vascular tree. The adult human body contains at least one trillion endothelial cells, which weigh more than 100 g and cover a surface area of more than 3000 square meters [1,2]. They therefore constitute a distributed organ that forms a dynamic interface with all other organs in the body.

The endothelium mediates vasomotor tone, regulates cellular and nutrient trafficking, maintains blood fluidity, contributes to the local balance between pro- and anti-inflammatory mediators as well as procoagulant and anticoagulant activity, participates in generation of new blood vessels, orchestrates organ development, participates in innate and acquired immunity, interacts with circulating blood cells, and undergoes programmed cell death [3,4]. Each of these activities is dynamically regulated in both space and time. Because endothelial cells receive cues from a wide variety of cells and tissues, they possess disparate properties that are specific to their local environment. Other phenotypic differences between endothelial cells are "locked in" by site-specific epigenetic mechanisms. Phenotypic heterogeneity is a central feature of the endothelium, and includes variations in morphology, biosynthetic repertoire, and behavior [5].

Here we review some of the general features of the endothelium [6].

Organ-specific considerations, which are presented separately, include:

The cardiovascular system – (See "Coronary artery endothelial dysfunction: Clinical aspects" and "Vascular endothelial function and fundamental mechanisms of fibrinolysis (thrombolysis)", section on 'Vascular endothelium'.)

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Literature review current through: Nov 2017. | This topic last updated: Jul 13, 2017.
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