EFFECT OF VASCULAR CONVEXITY ON DIFFUSIVE DELIVERY OF BLOOD-BORNE SUBSTANCES IN NORMAL AND TUMOR TISSUES

摘要

Blood-borne substances such as oxygen, nutrients, drugs and particles arrive at targeted tissues through a multi-step process that begins with convection along the blood vessels and then movement from the blood vessels to the surrounding tissues by convection through the cellular interstices or molecular diffusion. Interstitial convection may be important in the margins of tumors where highly permeable blood vessels encounter high transmural pressures, but otherwise, transport from the blood vessels to the tissues progresses primarily by diffusion. The vasculature in solid tumors is distinguished from that in normal tissues by being highly irregular, leaving avascular spaces of many sizes - some of them much larger than found in normal tissue. Normal vasculature, in contrast, has some randomness, but is often characterized by the classical Krogh cylinder model that assumes parallel capillaries arranged in a regularly-spaced lattice. More realistically, tumor and normal vasculatures fall along a spectrum between random and regular.