Fluid compartments
The
About two-thirds of the
The normal processes by which life self-regulates its biochemistry (homeostasis) produce fluid balance across the fluid compartments. Water and electrolytes are continuously moving across barriers (eg, cell membranes, vessel walls), albeit often in small amounts, to maintain this healthy balance. The movement of these molecules is controlled and restricted by various mechanisms. When illnesses upset the balance, electrolyte imbalances can result.
The interstitial and intravascular compartments readily exchange water and solutes, but the third extracellular compartment, the transcellular, is thought of as separate from the other two and not in dynamic equilibrium with them.[2]
The science of fluid balance across fluid compartments has practical application in intravenous therapy, where doctors and nurses must predict fluid shifts and decide which IV fluids to give (for example, isotonic versus hypotonic), how much to give, and how fast (volume or mass per minute or hour).
Intracellular compartment
The intracellular fluid (ICF) is all fluids contained inside the cells, which consists of cytosol and fluid in the cell nucleus.[3] The cytosol is the matrix in which cellular organelles are suspended. The cytosol and organelles together compose the cytoplasm. The cell membranes are the outer barrier. In humans, the intracellular compartment contains on average about 28 liters (6.2 imp gal; 7.4 U.S. gal) of fluid, and under ordinary circumstances remains in osmotic equilibrium. It contains moderate quantities of magnesium and sulfate ions.
In the cell nucleus, the fluid component of the nucleoplasm is called the nucleosol.[4]
Extracellular compartment
The interstitial, intravascular and transcellular compartments comprise the extracellular compartment. Its
Intravascular compartment
The main intravascular fluid in mammals is
Interstitial compartment
The interstitial compartment (also called "tissue space") surrounds tissue cells. It is filled with
Transcellular compartment
The transcellular fluid is the portion of total body fluid that is formed by the secretory activity of epithelial cells and is contained within specialized epithelial-lined compartments. Fluid does not normally collect in larger amounts in these spaces,
Fluid shift
Fluid shifts occur when the body's fluids move between the fluid compartments. Physiologically, this occurs by a combination of
Third spacing
"Third spacing" is the abnormal accumulation of fluid into an extracellular and extravascular space. In medicine, the term is often used with regard to loss of fluid into interstitial spaces, such as with
Patients who undergo long, difficult operations in large surgical fields can collect third-space fluids and become intravascularly depleted despite large volumes of intravenous fluid and blood replacement.
The precise volume of fluid in a patient's third spaces changes over time and is difficult to accurately quantify.
Third spacing conditions may include
are theoretically forms of third spacing, but the volumes are too small to induce significant shifts in blood volumes, or overall body volumes, and thus are generally not referred to as third spacing.See also
- Blood–brain barrier
- Compartment (pharmacokinetics)
- Distribution (pharmacology) and volume of distribution
References
- ISBN 978-1-60913-427-3.
- PMID 19653435.
- ^ Liachovitzky, Carlos (2015). "Human Anatomy and Physiology Preparatory Course" (pdf). Open Educational Resources. CUNY Academic Works: 69. Archived from the original on 2017-08-23. Retrieved 2021-06-22.
- PMID 4417675.
A soluble fraction of rat liver nuclei (nucleosol) was...
- ^ "Fluid Physiology: 2.1 Fluid Compartments".
- ISBN 978-0-7817-7909-8. Retrieved 9 June 2010.
- S2CID 19554202.
- ISBN 0-7216-9257-5. [1]
- ^ "FLUID AND ELECTROLYTE THERAPY". Archived from the original on 2010-07-07. Retrieved 2010-06-08.