The Tunica Intima is the innermost layer of blood vessels, including arteries and veins. It consists of a thin layer of endothelial cells that line the lumen, or interior space, of the vessel. This layer plays a crucial role in maintaining a smooth surface for blood flow and regulating interactions between the blood and the vessel wall. In addition to endothelial cells, the Tunica Intima contains a subendothelial layer made of connective tissue. This layer provides structural support and can influence vascular function. Proper functioning of the Tunica Intima is essential for cardiovascular health, as damage to this layer can lead to conditions like atherosclerosis.