The body fluids
The volume of total body water and body weight
The volume of total body water is approximately 60% of body weight in men and 50% in women.
The goal of homeostasis is to provide an optimal fluid environment for cellular function. The body fluids are divided into two major functional compartments:
2. The fluid outside cells is the extracellular fluid (ECF) is subdivided into the interstitial fluid and the blood plasma.
About 60% of total body water is ICF and 40% is ECF. Approximately 80% of ECF is interstitial fluid and the remaining 20% is blood plasma, which is contained inside the vascular system.
Body fluid compartments
Intracellular fluid (ICF) is separated from extracellular fluid (ECF) by cell membranes. ECF is composed of the interstitial fluid bathing cells and the blood plasma within the vascular system. Interstitial fluid is separated from plasma by capillary endothelia. Transcellular fluid is part of the ECF and includes epithelial secretions such as the cerebrospinal and extraocular fluids. ECF has a high [Na+] and a low [K+], whereas the opposite is true of ICF.
The concept of an internal environment in the body correlates with the interstitial fluid bathing cells.
Conclusion:
Homeostasis is ability to maintain a stable composition of interstitial fluid .
There is free exchange of water and small solutes between interstitial fluid and plasma across the blood capillaries.
In contrast, the exchange of most substances between interstitial fluid and intracellular fluid is highly regulated and occurs across plasma cell membranes.
Differences of ICF and ECF
