Oxygen And Tissues

The physiological concentrations of dissolved oxygen in tissues other than the lung are situated in the range 20-120^M (1Torr = 1.4^M). In reality in organs, tissue O2 tensions depend on the proximity of arterioles and capillaries as suppliers of oxygen. Oxygen concentrations are the most elevated in the blood of arteries, arterioles and the lowest in venules and veins. The O2 tension in a given tissue depends on the level of consumption of O2 by this tissue, on the local blood stream, on the relative distance of the zone considered from the nearest arteriole and capillary. Indeed, O2 consumption causes pO2 to fall rapidly between arterioles and veinules. This emphasises the fact that in tissues there is a distribution of oxygen tensions according to a gradient. Such a gradient also exists at the level of the cell such as in the mitochondrion, the terminal place of oxygen consumption where, O2 concentrations range from 1.5 to 3 ^M.

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