tomography that also gives 3D imaging. Function The vasa vasorum are found in large veins and arteries such as the aorta and its branches. These small vessels serve to provide blood supply and nourishment for tunica adventitia and outer parts of tunica media of large vessels. Clinical significance In the human descending aorta, vasa vasorum cease to supply the arterial tunica media with oxygenated blood at the level of the renal arteries. Thus, below this point, the aorta is dependent on diffusion for its metabolic needs, and is necessarily markedly thinner. This leads to an increased likelihood of aortic aneurysm at this location, especially in the presence of atherosclerotic plaques. Other species, such as dogs, do have vasa vasorum below their renal vasculature, and aneurysms at this site are substantially less likely. Cerebral blood vessels are devoid of vasa vasorum; however, these vessels have rete vasorum, which have similar function to vasa vasorum. A relationship exists between changes in the vasa vasorum and the development of atheromatous plaques. It is not understood whether changes in the vasa vasorum, especially in terms of their appearance and disappearance, is a cause or merely an effect of disease processes. In 2017 Haverich proposed that the formation of plaques is not from inside the vessel, but the result of inflammation of the vasa vasorum. Haverich noted that arteries fed by vasa vasorum are subject to development of arteriosclerotic plaques. He postulated that inflammation compromises the integrity of the arterial wall. He noted that arteries with thin walls, not having vasa vasorum, do not develop arteriosclerosis. Damage by inflamed vasa vasorum leads to cell death within the wall and subsequent plaques formation. Vasa vasorum inflammation can be caused by viruses, bacteria, and fine dust among others. According to his view this concept conforms to observations that cardiac infarctions are more common when influenza has occurred or fine particles have been inhaled. Small vessels like vasa vasorum and vasa nervorum are particularly susceptible to external mechanical compression, and thus are involved in pathogenesis of peripheral vascular and nerve diseases. A tear in vasa vasorum situated in tunica media layer of aorta may start pathologic cascade of events leading to aortic dissection. Presence of corkscrew collateral vessels in vasa vasorum is a hallmark of Buerger's disease and distinguishes it from Raynaud's phenomenon. T cells found near vasa vasorum are implicated in pathogenic process of giant cell arteritis.