Introduction Volker Nickeleit, M.D. J. Charles Jennette, M.D.

1) Anatomy of Normal Blood Vessels This short course will deal with blood vessels and not lymphatic vessels, and thus will focus on pathologic changes in arteries, arterioles, capillaries, venules and veins. All arteries and arterioles have an intima, media and adventitia. In normal vessels, there is little or no separation of endothelial cells from the underlying elastica interna or muscularis. With aging and in many pathologic conditions, there is a thickening of the intima by the deposition of connective tissue. Large elastic arteries have large amounts of elastic tissue in the media. These include the aorta and the brachiocephalic, subclavian, beginning of common carotid, and pulmonary arteries. Medium sized and large arteries have an internal and external elastic lamina on either side of a well-developed media that is composed predominantly of smooth muscle (muscularis media) except in elastic arteries. Small arteries have an internal elastic lamina but no well-defined external elastic lamina. Arterioles have no identifiable internal or external elastic lamina, and have 1 to 2 layers of smooth muscle cells in the media. With aging, especially if accompanied by hypertension, amorphous proteinaceous material (hyaline) may accumulate in the intima and muscularis of arterioles. Capillaries are lined by endothelial cells that have specialized structure in certain locations, such as the fenestrated endothelium of the renal glomerular and pulmonary alveolar capillaries. Venules also have specialized endothelium in certain locations, such as the high endothelium at sites of lymphocyte trafficking. 2) Diagnostic Classification of Diseases of Blood Vessels Diseases of blood vessels can be categorized on the basis of pathologic features, types and location of involved vessels, associated clinical or pathologic syndromes, and known or putative pathogenic mechanisms. In fact, many diagnostic categories are defined by combinations of these features. The incomplete list below is one approach to categorizing vascular disease based on combinations of pathologic and pathogenic criteria: Inflammatory Vascular Diseases (Vasculitides) Infectious Bacterial Rickettsial Viral Fungal Noninfectious Large vessel vasculitis (chronic granulomatous arteritis) Medium-sized vessel vasculitis (necrotizing arteritis) Small vessel vasculitis (necrotizing polyangiitis) Phlebitis Atherosclerosis Noninflammatory Vascular Diseases (Vasculopathies) Chronic hypertensive vasculopathy Thrombotic microangiopathies Thrombotic coagulopathies Amyloidosis Monoclonal immunoglobulin deposition diseases Fibromuscular dysplasia Metabolic storage diseases