Endothelial tissue is a thin layer of cells that lines the interior surface of blood vessels, including arteries, veins, and capillaries. This tissue plays a crucial role in maintaining vascular health by regulating blood flow, preventing blood clotting, and controlling the exchange of substances between the bloodstream and surrounding tissues. Additionally, endothelial cells produce various substances that influence blood pressure and inflammation. They are essential for the formation of new blood vessels, a process known as angiogenesis, and are involved in the body's response to injury and infection, making them vital for overall cardiovascular function.