Intima elastic lamina

The normal arterial wall consists of the intima, media, and adventitia, as illustrated in Fig. 4—3A. The endothelium is located in the intima and consists of a layer of endothelial cells that line the lumen of the artery and form a selective barrier between the vessel wall and blood contents. The internal elastic lamina separates the intima and media, where vascular smooth muscle cells are found. The vascular adventitia comprises the artery s outer layer. Atherosclerotic lesions form in the subendothelial space between the endothelial cells and internal elastic lamina. 

The normal artery wall is composed of three layers intima, media, and adventita (Figure 20-10). On the luminal side, the intima contains a single layer of endothelial cells. These cells permit passage of water and other substances from blood into tissue cells. On the peripheral side, the intimal layer is surrounded by a fenestrated sheet of elastic fibers (the internal elastic lamina). The middle portion of the intimal layer contains various extracellular components of connective tissue matrix and fibers and occasional smooth cells, depending on the type of artery, and the age and sex of the subject. 

The normal artery is composed of three distinct layers (Fig. 34.21). That which is closest to the lumen of the vessel, the intima, is lined by a monolayer of endothelial cells that are bathed by the circulating blood. Just beneath these specialized cells lies the subintimal extracellular matrix, in which some vascular smooth muscle cells are embedded (the subintimal space). The middle layer, known as the tunica media, is separated from the intima by the internal elastic lamina. The tunica media contains lamellae of smooth muscle cells surrounded by an elastin- and collagen-rich matrix. The external elastic lamina forms the border between the tunica media and the outermost layer, the adventitia. This layer contains nerve fibers and mast cells. It is the origin of the vasa vasorum, which supply blood to the outer two thirds of the tunica media. 

Wall morphology Complete tunica adventitia, external elastic lamina, tunica media, internal elastic lamina, tunica intima. ... 

Complete tunica adventitia, external elastic lamina, tunica media, internal elastic lamina, tunica intima, subendothelium, endothelium, and vasa vasorum vascular supply Main branches 32 5 mm-2.25 cm 3.3-6 cm —2 mm 83.2 ml... 

In 1971, we were able to demonstrate the presence of serum beta-lipoprotein in the edematous parts of aortic wall showing the edematous arterial reaction (25,29,34). Namely just a few hours after a single dose treatment of animals with cholesterol, particles like beta-lipoprotein with diameters between 150-250A infiltrated into the intima and further down to the media. The mode of infiltration was such that the particles entered the sub-endothelial space first, temporarily dammed by the internal elastic lamina, then into the muscular layers via pores in the internal elastic lamina, and eventually have been carried away possibly through lymphatic channels (25,29,34). The PDC has proved itself to sufficiently reduce or prevent this infiltrative process to occur (25,34). At this juncture, we were faced upon with the underlying mechanism that can possibly provide an explanation as to why the large particles such as beta-lipoprotein could be transported into the subendothelial layer so rapidly that is almost instantaneous. 

---