Knowra Endothelium Endothelium The endothelium is a thin layer of cells lining blood vessels, lymphatic vessels, and the heart. It regulates exchange, blood flow, clotting, and immune-cell passage.
Endothelial barrier : The selectively permeable boundary formed by endothelial cells and their junctions. It controls which fluids, molecules, and cells pass between blood and surrounding tissues.
Vascular endothelium : The endothelial lining of blood vessels, including arteries, veins, and capillaries. It is the specialized form lining the blood vessels named in this concept.
Endothelial dysfunction : Impaired endothelial regulation of vascular tone, barrier function, inflammation, or clotting. It describes loss of the functions that healthy endothelium normally performs.
Vascular smooth muscle : Contractile cells in vessel walls that regulate vessel diameter and blood pressure. Unlike the luminal endothelium, these cells form a deeper layer that constricts or relaxes vessels.
Vasodilation : An increase in blood-vessel diameter caused by relaxation of vascular smooth muscle. Endothelial signals such as nitric oxide relax nearby smooth muscle and widen vessels.
Lymphatic endothelium : The endothelial lining of lymphatic vessels and lymphatic organs. Its distinctive structure supports fluid uptake and movement of immune cells.
Atherosclerosis : A chronic artery disease involving lipid-rich plaques in the arterial wall. Endothelial injury and dysfunction contribute to plaque development and progression.
Tunica adventitia : The outer connective-tissue layer of a blood vessel wall. It lies outside the endothelium and smooth-muscle layers, anchoring and supporting the vessel.
Nitric oxide : A small signaling molecule that regulates vascular tone, platelet activity, and other processes. Endothelial cells release it to promote vessel relaxation and limit platelet adhesion.
Endocardium : The inner lining of the heart chambers and valves, continuous with vascular endothelium. It is the heart-lining tissue included in the concept's definition.
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