The Microscopical Appearances of Human Peripheral Arteries during Growth and Aging.

Twelve peripheral arteries are described in 59 patients of all ages. Accumulation of ground substance in the media, accompanied by small foci of calcification of the internal elastic lamina, was found in the large leg arteries of young adults, and progressively in a wider series of arteries throughout life. This picture showed no relationship to hypertension, to Mönckeberg's sclerosis, or to the development of atheroma. A notable quantity of ground substance may be a feature of early intimal development, and of a thickened intima in adult life, and probably the major constituent of an organizing thrombus. Organizing thrombi were apparently incidental findings at several sites even in young adults, and showed no association with the state of the arterial wall beneath the lesion, the wall being in fact normal, though accumulated mucopolysaccharide was always present. Atheroma increases with age, and its focal incidence gives way to confluence in the arteries of the leg. Occlusive peripheral artery atheroma was found only in cases where the cause of death was severe atheroma, e.g., coronary artery disease and abdominal aortic aneurysm, or in myxoedema, in which the incidence of occlusive lesions may differ from that in severe generalized atheroma. Elastic tissue is described in all coats of the artery wall, with some variants of the common pattern. The musculo-elastic cushion is not seen after adolescence, and it is suggested that the cushion represents the growing point of the artery. Longitudinal muscle bundles are almost confined to the popliteal artery, where they may form an essential buttress for a large branching artery subject to unusual external stresses. The functions and origin of the ground substance are discussed.