extracellular fluid (ECF), the portion of the body fluid comprising the interstitial fluid and blood plasma. The adult body contains about 11.2 L of interstitial fluid, constituting about 16% of body weight, and about 2.8 L of plasma, constituting about 4% of body weight. Plasma and interstitial fluid are very similar chemically and, in conjunction with intracellular fluid, help control the movement of water and electrolytes throughout the body. Some of the important ionized components of extracellular fluid are protein, magnesium, potassium, chlorine, calcium, and certain sulfates.
