has part has part surrounded by surrounded by adjacent to adjacent to endothelium tunica media tunica intima https://upload.wikimedia.org/wikipedia/commons/3/32/Illu_artery.jpg SCTID:87483006 SCTID:8361002 intima NCIT:C33820 MESH:D017539 The tunica intima (or just intima) is the innermost layer of an artery or vein. It is made up of one layer of endothelial cells and is supported by an internal elastic lamina. The endothelial cells are in direct contact with the blood flow. The inner coat (tunica intima) can be separated from the middle by a little maceration, or it may be stripped off in small pieces; but, on account of its friability, it cannot be separated as a complete membrane. It is a fine, transparent, colorless structure which is highly elastic, and, after death, is commonly corrugated into longitudinal wrinkles. The inner coat consists of: A layer of pavement endothelium, the cells of which are polygonal, oval, or fusiform, and have very distinct round or oval nuclei. This endothelium is brought into view most distinctly by staining with silver nitrate. A subendothelial layer, consisting of delicate connective tissue with branched cells lying in the interspaces of the tissue; in arteries of less than 2 mm. in diameter the subendothelial layer consists of a single stratum of stellate cells, and the connective tissue is only largely developed in vessels of a considerable size. An elastic or fenestrated layer, which consists of a membrane containing a net-work of elastic fibers, having principally a longitudinal direction, and in which, under the microscope, small elongated apertures or perforations may be seen, giving it a fenestrated appearance. It was therefore called by Henle the fenestrated membrane. This membrane forms the chief thickness of the inner coat, and can be separated into several layers, some of which present the appearance of a network of longitudinal elastic fibers, and others a more membranous character, marked by pale lines having a longitudinal direction. In minute arteries the fenestrated membrane is a very thin layer; but in the larger arteries, and especially in the aorta, it has a very considerable thickness. [WP,unvetted].[Wikipedia] GAID:523 the FMA class represents a more generic layer which is the superclass of the layer found in both blood vessels and lymph vessels (and also endocardium) - we should probably follow this structure the FMA class represents a structure which may have both epithelium and fibroelastic connective tissue as parts EMAPA:36297 MA:0002861 BTO:0002012 FMA:55589 UBERON:0002523 Wikipedia:Tunica_intima UMLS:C0162864 The innermost layer of a blood vessel which is a lining of endothelial cells facing the lumen[Kardong]. tunica intima vasorum Bichat's tunic organ component layer lumen of blood vessel