Oxygen Cascade Essay Example | Topics and Well Written Essays - 3250 words

Oxygen Cascade - Essay Example Any disease which affects oxygen supply and access at the cellular level therefore has potentially fatal consequences, even if the disorder is transient. Oxygen does not normally exist in nature by itself, but rather in mixture with other gases (Townsend, and Webster, 2000). Dalton's Law therefore comes in to play at all times, with each gas in a mixture exerting an independent partial pressure (Hopley, and Schalkwyk, 2006). Nitrogen, carbon dioxide, and water vapor are three common gases which generally accompany oxygen during crucial phases of respiration. Living cells may therefore be unable to access oxygen in a state of disease, even though the gas is available in the surroundings. Oxygen availability and demand for this substance are not steady at all times. Physical activity and other physiological processes, including those affected by disease, may cause oxygen demand to peak well over the average level. The partial pressure of oxygen, on the other hand, may fall off steeply, as at high altitudes. Changes in oxygen availability and demand do not necessarily move in tandem. High altitude sickness is a common example of oxygen demand peaking even as its partial pressure falls steeply. Disease may also affect the supply/demand balance of oxygen at the tissue or cellular levels. There is a complicated and inter-related delivery system for oxygen from the atmosphere external to a living being and the mitochondria in cells responsible for oxidative phosphorylation (Lewis, and Fitz-Henry, 2001). Any defect in a tissue, structure, or a system, involved in respiration, circulation, diffusion, or metabolism, can affect the ability to use oxygen for vital processes. This paper defines the series of partial pressures at which oxygen is available at various levels of a living system, and relates the processes involved in the procurement, gaseous exchange, transport, and use of oxygen, to states of disease. Steps in the Oxygen Cascade Most people live at or around sea level. The atmospheric pressure at this level is 760 mmHg and 20.94% of air at this altitude is oxygen (Neligan, 2002). Therefore, the partial pressure of oxygen (PO2) at sea level is 159 mmHg. However, the PO2 at the level mitochondria in cells is as low as 3 mmHg (Neligan, 2002). Where have 156 mmHg gone The vast proportion of oxygen is either diluted or even lost altogether as it travels in to lungs and from the alveoli to blood in the circulatory system. The various stages by which the partial pressure of oxygen falls off are collectively known as the oxygen cascade. Life has evolved to deal with such colossal inefficiencies, and to maintain normal health at the same time. The transfer of oxygen from air to blood in the lungs, the transport of oxygen by blood to organs and to tissues, and the diffusion of oxygen from capillaries to individual cells and to the mitochondria inside them, all take place within specific ranges of partial pressures. H owever, the balances are delicate, and diseases and other may have serious effects on the oxygen cascade. All diseases which affect the structure and functioning of the lungs, or which affect the capacity of blood to transport oxygen, or which affect circulation of blood to the far reaches of the body, or which affect cellular organization, especially in terms of mitochondrial