endothelial cell
Meaning of endothelial cell: The single layer of flat cells lining every vessel, acting as a non-stick surface and as a control panel for blood flow.
Definition of endothelial cell
An endothelial cell is one of the flat cells that form the inner lining of blood vessels, lymph vessels and the chambers of the heart. Laid edge to edge in a single layer, they create a smooth surface that blood does not clot on. They also release chemicals that widen or narrow the vessel, control what passes into surrounding tissue, and decide where immune cells leave the circulation.
What does this lining actually do?
It is far from a passive wallpaper. The layer, called the endothelium, is one of the largest tissues in the body when the whole vascular network is counted, and it runs several separate jobs at once.
| Job | How it works |
|---|---|
| Prevent clotting | A smooth surface plus anticlotting molecules |
| Control vessel width | Releases nitric oxide to relax the muscle around it |
| Gatekeeping | Junctions between cells decide what crosses |
| Immune traffic | Displays sticky proteins where white cells should exit |
| New vessel growth | Divides and migrates to form capillaries |
Are they the same everywhere?
No, and the differences are deliberate. In the kidney and in glands the layer is perforated with pores, so fluid and small molecules pass freely. In the liver and bone marrow the gaps are larger still, allowing whole cells through. At the opposite extreme, the vessels of the brain have exceptionally tight seals between neighboring cells, and that arrangement is the physical basis of the blood brain barrier. Lymph vessels have their own version, with overlapping flaps that let tissue fluid in but not back out.
What happens when they stop working properly?
Endothelial dysfunction is an early step in artery disease, arriving before any narrowing can be seen. Less nitric oxide is released, so vessels do not relax as they should and blood pressure tends to rise. The surface becomes sticky instead of slippery, so white cells attach and burrow into the wall, which is how a fatty plaque begins. Smoking, high blood sugar, high cholesterol and raised pressure all damage this layer, which is part of why those risks converge on the same diseases. Severe infection injures endothelium throughout the body at once, producing leaking vessels, tissue swelling and widespread clotting.
Also known as
Used in a sentence
The specimen showed endothelial cell loss along the affected segment.
Good to know
Damage to the endothelium precedes visible narrowing in artery disease, which is why smoking, high blood sugar, raised cholesterol and high blood pressure share the same end result.
Word origin
Where “endothelial cell” comes from
From the Greek endon, meaning within, with thele, a nipple or delicate tissue, giving endothelium, the inner lining.