Aspartame is the most controversial food additive in history, and its approval for use in food was the most contested in FDA history. In the end, the artificial sweetener was approved, not on scientific grounds, but rather because of strong political and financial pressure.
The arterioles then divide further into capillaries. Capillaries are the smallest blood vessels and their walls are only one cell thick which allows diffusion between the blood and cells to occur. Nutrients and oxygen from the blood diffuses through the capillary walls into the tissues that need it. This is aided by the relatively high blood pressure that also squeezes the oxygen and nutrients through the capillary wall and into the cells of the tissue.
Tissues vary considerably in their sensitivity to hypoxia. Neurological cells tolerate hypoxia for only a few minutes. whereas bladder smooth muscle may survive for several days. without oxygen. This has important implications in the. management of oxygen transport and monitoring of tissue. hypoxia in critically ill patients. Oxygen transport. Delivery to organs and tissues. The mechanisms controlling oxygen distribution are. incompletely understood but involve a series of convective and. diffusive processes.