Endothelial cells are specialized cells that line the interior surface of blood vessels, including arteries, veins, and capillaries. They form a barrier between the blood and surrounding tissues, playing a crucial role in regulating blood flow, inflammation, and the exchange of substances. These cells are essential for maintaining vascular health and function. In addition to their structural role, endothelial cells produce various substances that help control blood pressure and prevent blood clotting. They also respond to signals from the body, such as those from the immune system, to help manage responses to injury or infection, contributing to overall cardiovascular health.