+ + electrolytes
----> direction of water flow (osmosis)
Figure 2-3. Tonicity (cell with semipermeable membrane, nonpermeable to
electrolytes present).
a. Hypertonicity. If the overall concentration of electrolytes is greater in the
tissue fluid surrounding a cell than it is in the intracellular fluid within the cell, the tissue
fluid is hypertonic (noun: hypertonicity). The cell tends to be destroyed by loss of its
fluid to the hypertonic environment.
b. Hypotonicity. If the overall concentration of electrolytes as less in the tissue
fluid than it is in the intracellular fluid within the cell, the tissue fluid is hypotonic (noun:
hypotonicity). In a hypotonic environment, fluid will enter a cell and cause it to swell
and burst.
c. Isotonicity. If the concentrations of electrolytes are the same in the tissue
fluid and the intracellular fluid, the situation is balanced (homeostatic). That is, the fluids
are isotonic.
MD0007
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