The Arterial Wall [antikvár]

One of the expedient methods for deseribing the circulatory system is to draw an analogy between it and a plumbing system. On occasion one sees the heart illustrated by a mechanical pump and the arteries and veins simulated by an intricate layout of pipes. Even beyond elementary presentations there is a tendency to treat blood vessels as little more than conducting tubes. This, of course, is not so. Blood vessels, arteries in particular, are hard working organs with personalities of their own. They have distinctive susceptibilities to disease, vary in structure, and age at different rates. It is well known that atheromatosis induced in rabbits by cholesterol feeding appears in somé arteries and not in others, and in humans atherosclerosis normally does not appear in the pulmonary artery. Although most muscular arteries are characterized by the presence of an elastica interna and an elastica externa, the latter is lacking in the umbilical and cerebral arteries. On the other hand, the cerebral artery possesses a distinctive hypertrophied elastica interna. We now know that arteries, as might well be expected, are metabolically active organs; cholesterol is synthesized in arteries, a number of enzyme systems have been demonstrated, and at least a portion of the arterial wall contains a circulation of its own. Concern with the normál structure, chemistry, and function of arteries as well as the aging thereof is much more than an academic matter. Since antibiotics greatly reduced infectious diseases a greater fraction of our population reaches adulthood and senility. Approximately two out of three aduit deaths are caused, directly or indirectly, by cardiovascular disease. Atherosclerosis in the coronary and cerebral arteries has very grave consequences. Although the current fashion is to treat atherosclerosis as a disease of cholesterol metabolism or the manner of its transport, it is reasonable to believe that an appreciation of the biology of arteries will facilitate understanding of the etiology of this disease.