How much TBW is contained in the extracellular fluid?

How much TBW is contained in the extracellular fluid?

• A. Approximately 2/3 of total body water
• B. Approximately 1/3 of total body water
• C. Approximately 1/2 of total body water
• D. Approximately 1/4 of total body water

Answer: (B)

Fluid compartments are unevenly distributed. Total body water is about 60% of body weight, and roughly two-thirds of that is inside cells (intracellular fluid), leaving about one-third outside cells (extracellular fluid). So the extracellular fluid accounts for about 1/3 of total body water. In a typical adult, that corresponds to roughly 14 liters of ECF out of about 42 liters of TBW, with most of the ECF in the interstitial space and a smaller portion in plasma, plus a small transcellular component.

Fluid compartments are unevenly distributed. Total body water is about 60% of body weight, and roughly two-thirds of that is inside cells (intracellular fluid), leaving about one-third outside cells (extracellular fluid). So the extracellular fluid accounts for about 1/3 of total body water. In a typical adult, that corresponds to roughly 14 liters of ECF out of about 42 liters of TBW, with most of the ECF in the interstitial space and a smaller portion in plasma, plus a small transcellular component.