<P> The third extracellular compartment, the transcellular, consists of those spaces in the body where fluid does not normally collect in larger amounts, or where any significant fluid collection is physiologically nonfunctional . Examples of transcellular spaces include the eye, the central nervous system, the peritoneal and pleural cavities, and the joint capsules . A small amount of fluid, called transcellular fluid, does exist normally in such spaces . For example, the aqueous humor, the vitreous humor, the cerebrospinal fluid, the serous fluid produced by the serous membranes, and the synovial fluid produced by the synovial membranes are all transcellular fluids . They are all very important, yet there is not much of each . For example, there is only about 150 mL of cerebrospinal fluid in the entire central nervous system at any moment . All of the aforementioned fluids are produced by active cellular processes working with blood plasma as the raw material, and they are all more or less similar to blood plasma except for certain modifications tailored to their function . For example, the cerebrospinal fluid is made by various cells of the CNS, mostly the ependymal cells, from blood plasma . </P> <P> Fluid shifts occur when the body's fluids move between the fluid compartments . Physiologically, this occurs by a combination of hydrostatic pressure gradients and osmotic pressure gradients . Water will move from one space into the next passively across a semi permeable membrane until the hydrostatic and osmotic pressure gradients balance each other . Many medical conditions can cause fluid shifts . When fluid moves out of the intravascular compartment (the blood vessels), blood pressure can drop to dangerously low levels, endangering critical organs such as the brain, heart and kidneys; when it shifts out of the cells (the intracellular compartment), cellular processes slow down or cease from intracellular dehydration; when excessive fluid accumulates in the interstitial space, oedema develops; and fluid shifts into the brain cells can cause increased cranial pressure . Fluid shifts may be compensated by fluid replacement or diuretics . </P> <P> "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 burns or edema, but it can also refer to fluid shifts into a body cavity (transcellular space), such as ascites and pleural effusions . With regard to severe burns, fluids may pool on the burn site (i.e. fluid lying outside of the interstitial tissue, exposed to evaporation) and cause depletion of the fluids . With pancreatitis or ileus, fluids may "leak out" into the peritoneal cavity, also causing depletion of the intracellular, interstitial or vascular compartments . </P> <P> 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 . </P>

Where is fluid found such as intracellular etc and how is albumin important