Fluid Pressures/Movements (Starling's Law)

• ECF and ICF fluid shifts occur related to changes in pressure within the compartments

• Fluid flows only when there is a difference in pressure

Osmolality:

• Concentration of a solution determined by the number of dissolved particles per kilogram of water. Controls water movement and distribution in body fluid compartments (275-295mmol/L)

Movement of Body Fluids and Electrolytes Solutes (substances dissolved in a liquid)

Crystalloids (salts that dissolve readily into true solutions)

Colloids (substances such as large protein molecules that do not readily dissolve into true solutions)

Solvent (is the component of a solution that can dissolve a solute)

Materials are transported between cellular and extracellular spaces through several routes including:

• Diffusion

• Osmosis

• Filtration

• Active transport

Routes of Transport of Body Fluid Diffusion:

• Water move across a semi permeable membrane from an area of high solute concentration to one of lower solute concentration.



Osmosis:

• Movement of water across a semi permeable membrane from a less concentrated solution to a more concentrated solution thereby.



Filtration:

• Fluids and solutes move together across a membrane from an area of higher pressure to an area of a lower pressure.



Active Transport:

• Movement of solutes across cell membranes from a less concentrated solution to a more concentrated solution.

• Importance in maintaining the differences in sodium and potassium ion concentration of ECF and ICF.

• Na+ concentration are higher in ECF and K+ concentrations are higher in ICF .

• To maintain these proportions, an active transport mechanism (Na+- K+ pump) is activated.



Diffusion vs Active Transport: