PATHOLOGY

Detailed explanation-1: -Endothelial cells are arguably the most important component of the tunica intima and form the primary barrier between blood and tissue. They are highly specialized cell type and cover the luminal surface of the tunica intima. Endothelial cells have a number of critical functions.

Detailed explanation-2: -The innermost layer of the vein is the tunica intima. This layer consists of flat epithelial cells. These cells allow fluid to flow smoothly and are interspersed with valves that ensure the flow continues in one direction. This continuous layer of epithelial cells holds cells and fluid within the vessel lumen.

Detailed explanation-3: -The innermost layer, the tunica intima (also called tunica interna), is simple squamous epithelium surrounded by a connective tissue basement membrane with elastic fibers. The middle layer, the tunica media, is primarily smooth muscle and is usually the thickest layer.