Endothelium

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Endothelium
Diagram showing the location of endothelial cells
Transmission electron micrograph of a microvessel showing endothelial cells, which encircle an erythrocyte (E), forming the innermost layer of the vessel, the tunica intima.
Details
System	Circulatory system
Location	Lining of the inner surface of blood vessels and lymphatic vessels
Identifiers
MeSH	D004727
TH	H2.00.02.0.02003
FMA	63916
Anatomical terms of microanatomy [edit on Wikidata]

The endothelium (pl.: endothelia) is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels.^[1] The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the vessel wall.

Endothelial cells in direct contact with blood are called vascular endothelial cells whereas those in direct contact with lymph are known as lymphatic endothelial cells. Vascular endothelial cells line the entire circulatory system, from the heart to the smallest capillaries.

These cells have unique functions that include fluid filtration, such as in the glomerulus of the kidney, blood vessel tone, hemostasis, neutrophil recruitment, and hormone trafficking. Endothelium of the interior surfaces of the heart chambers is called endocardium. An impaired function can lead to serious health issues throughout the body.