Page 236 - Saunders Comprehensive Review For NCLEX-RN

b. Diffusion of a solute spreads the
molecules from an area of higher
concentration to an area of lower
concentration.
c. A permeable membrane allows
substances to pass through it without
restriction.
d. A selectively permeable membrane
allows some solutes to pass through
without restriction but prevents other
solutes from passing freely.
e. Diffusion occurs within fluid
compartments and from one
compartment to another if the barrier
between the compartments is
permeable to the diffusing substances.
2. Osmosis
a. Osmosis is the movement of solvent
molecules across a membrane in
response to a concentration gradient,
usually from a solution of lower to one
of higher solute concentration.
b. Osmotic pressure is the force that
draws the solvent from a less
concentrated solute through a
selectively permeable membrane into a
more concentrated solute, thus tending
to equalize the concentration of the
solvent.
c. If a membrane is permeable to water
but not to all solutes present, the
membrane is a selective or
semipermeable membrane.
d. When a more concentrated solution is
on one side of a selectively permeable
membrane and a less concentrated
solution is on the other side, a pull
called osmotic pressure draws the water
through the membrane to the more
concentrated side, or the side with
more solute.
3. Filtration
a. Filtration is the movement of solutes
and solvents by hydrostatic pressure.
b. The movement is from an area of
higher pressure to an area of lower
pressure.
4. Hydrostatic pressure

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