The endothelium is the layer of cells that line the surface of the inside of the arteries and veins, the heart, and lymph vessels.The endothelium releases molecules, e.g. nitric oxide, angiotensin II, etc., that help to expand (dilate) or contract (constrict) the blood vessels and thus raise or lower blood pressure. The cells of the endothelium release substances (called factors) that help to maintain heart and blood vessel wall tone and that help to inhibit platelet aggregation and inflammation.
Why is this important? Coenzyme Q10 supplementation has been shown to improve endothelial function.