ABSTRACT
To remain viable and to maintain proper function, all living cells depend on an adequate supply of nutrients and the efficient removal of metabolic products. In all except the most primitive organisms, blood is the vehicle for transporting these substances and the blood vessels are the conduits. Lesions within the human arterial tree produce symptoms and signs only when the integrity of the vessel wall is violated, allowing blood to escape, or when transportation is impaired sufficiently to compromise the viability or function of the tissues. A level of blood flow that suffices under resting conditions may be inadequate under conditions of stress, such as exercise, trauma, or infection. Thus, while the physical dimensions of an obstructing lesion place limitations on the ability of the arteries to transport blood and the strength of the arterial wall determines its resistance to leakage, the needs of the recipient organs ultimately dictate the threshold for the appearance of symptoms.
