Fluid /Electrolyte Balance  Elmhurst College
Fluid Exchange Processes Fluid Exchange kidneys Fluid Deficit  Chemistry Department
Fluid Exchange in Tissues Fluid Excess    Virtual ChemBook

Compartments of
Body and Distribution of Water by Weight

Plasma 5%
Interstitial 15%

Intracellular 40%

Total 60 % Water

Solids - 40%
fat, protein, carbohydrates,
minerals

Fluid and Electrolyte Balance

The main fluid in the body is water. Total body water is 60% of body weight. The water is distributed in three main compartments separated from each other by cell membranes. The intracellular compartment is the area within the cell. The extracellular compartment consists of the interstitial area (between and around cells) and the inside of the blood vessels (plasma).

ELECTROLYTE DISTRIBUTION

 Electrolyte

 Extracellular
meq/liter

 Intracellular
meq/liter

Function

 Sodium  142  10  fluid balance, osmotic
pressure
 Potassium 5 100  Neuromuscular excitability
acid-base balance
 Calcium 5 - bones, blood clotting
 Magnesium 2 123 enzymes
 Total Positive ions  154 205  

Electrolyte Distribution

 Electrolyte

Extracellular
meq/liter

 Intracellular
meq/liter

 Function

 Chloride  105  2 fluid balance, osmotic pressure
 Bicarbonate 24 8 acid-base balance
 Proteins 16 55 osmotic pressure
 Phosphate 2 149 energy storage
 Sulfate 1 - protein metabolism
 Total Negative ions 154 205  

Electrolytes are the chemicals dissolved in the body fluid. The distribution has important consequences for the ultimate balance of fluids.

Sodium chloride is found mostly in extracellular fluid, while potassium and phosphate are the main ions in the intracellular fluid.