page_title: Extracellular fluid
section_title: Function
hierarchical_section_title: Extracellular fluid / Function
caption_attribution_description: English: The sodium-potassium pump and related diffusion of sodium and potassium between the extracellular and intracellular space.
context_page_description: Extracellular fluid denotes all body fluid outside the cells of any multicellular organism. Total body water in healthy adults is about 60% of total body weight; women and the obese typically have a lower percentage than lean men. Extracellular fluid makes up about one-third of body fluid, the remaining two-thirds is intracellular fluid within cells. The main component of the extracellular fluid is the interstitial fluid that surrounds cells.
  Extracellular fluid is the internal environment of all multicellular animals, and in those animals with a blood circulatory system, a proportion of this fluid is blood plasma. Plasma and interstitial fluid are the two components that make up at least 97% of the ECF. Lymph makes up a small percentage of the interstitial fluid. The remaining small portion of the ECF includes the transcellular fluid. The ECF can also be seen as having two components – plasma and lymph as a delivery system, and interstitial fluid for water and solute exchange with the cells.
  The extracellular fluid, in particular the interstitial fluid, constitutes the body's internal environment that bathes all of the cells in the body.
context_section_description: The extracellular fluid provides the medium for the exchange of substances between the ECF and the cells, and this can take place through dissolving, mixing and transporting in the fluid medium. Substances in the ECF include dissolved gases, nutrients, and electrolytes, all needed to maintain life. The ECF also contains materials secreted from cells in soluble form, but which quickly coalesces into fibres (e.g. collagen, reticular, and elastic fibres) or precipitates out into a solid or semisolid form (e.g. proteoglycans which form the bulk of cartilage, and the components of bone). These and many other substances occur, especially in association with various proteoglycans to form the extracellular matrix or the "filler" substance between the cells throughout the body. These substances occur in the extracellular space, and are therefore all bathed or soaked in ECF, without being part of the ECF.
caption: Sodium-potassium pump and the diffusion between extracellular fluid and intracellular fluid
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