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Unformatted text preview: s (e.g., anesthetics); fluid and electrolytes are also exchanged, in part, by diffusion forces (a in preceding figure). Fick's First Law of diffusion: Where dn/dt is flux in moles/sec, D is diffusion constant, A is surface area, DC is concentration difference, and DX is thickness of barrier to diffusion. The movement (or flux) of a molecule is directly related to its diffusion constant across the barrier, the surface area available for diffusion, and the concentration gradient across the barrier. In the case of O2 diffusing from the exchange vessels into the tissue, increasing the partial pressure of oxygen (pO2) in the plasma, or increasing the surface area for exchange (i.e., increasing the number of open capillaries), increases the total amount of O2 per unit time moving out of the blood and into the tissue. Bulk Flow (Convection) Bulk flow of fluid and electrolytes occurs through "pores" and intercellular clefts (d,e,f in preceding figure) This mechanism of exchange is particularly important in renal glomerular capillaries; however, it occurs to variable extent in nearly a...
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This note was uploaded on 04/18/2008 for the course PHYS 1010 taught by Professor Thompson during the Fall '07 term at New York Medical College.
- Fall '07
- Hydrostatic Pressure