Main Page | See live article | Alphabetical index The endothelial cell is a flattened cell type that forms a sheet (the endothelium) lining a blood vessel. Endothelial cells line the entire vascular system, from heart to the smallest capillary, and control the passage of materials - and the transit of white blood cells - into and out of the bloodstream. They repair and renew the lining of established blood vessels, and create new blood vessels. This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.