The extracellular fluids may be divided into three types: interstitial fluid in the 'interstitial compartment' (surrounding tissue cells and bathing them in a solution of nutrients and other chemicals), blood plasma and lymph in the 'intravascular compartment' (inside the blood vessels and lymphatic vessels), and small amounts of transcellular fluid such as ocular and cerebrospinal fluids in the 'transcellular compartment'. Ībout two thirds of the total body water of humans is held in the cells, mostly in the cytosol, and the remainder is found in the extracellular compartment. The intracellular compartment is the space within the organism's cells it is separated from the extracellular compartment by cell membranes. The two main fluid compartments are the intracellular and extracellular compartments. The human body and even its individual body fluids may be conceptually divided into various fluid compartments, which, although not literally anatomic compartments, do represent a real division in terms of how portions of the body's water, solutes, and suspended elements are segregated. For the concept of informal shared public space in community planning, see Third place. The physical barrier between the intracellular fluid and interstitial fluid is the cell plasma membrane, and the physical barrier between the interstitial fluid and plasma is the capillary endothelium.'Third space' redirects here. These fluid compartments are emphasized by the gray background color. If we examine this figure carefully, and if we consider the functional interconnections of the fluid compartments, it becomes clear that there are three major fluid compartments: (1) intracellular fluid, (2) interstitial fluid, and (3) plasma. Transcellular fluid generally comprises up to about 2.5% of the total body water (or up to ~1 L).

Cerebrospinal fluid (the fluid bathing the brain and the spinal cord), intraocular fluids (aqueous and vitreous humors), inner ear fluids (endolymph and perilymph), pericardial fluid, peritoneal fluid, synovial fluids (in joints), as well as some other fluids are components of the transcellular fluid in the body. This fluid is generally separated from the plasma by an additional epithelial layer in addition to the capillary endothelium. Transcellular fluid is found in small amounts in different body regions and, in total, comprises a very small portion (though not unimportant) of the total body water. It is generally about 75% of the volume of ECF (or ~10.5 L). Interstitial fluid is the fluid that directly bathes the cells and tissues in the body. The extravascular compartment is further subdivided into two compartments: interstitial fluid and transcellular fluid. The volume of plasma is about 3 L and is generally about 25% of the volume of ECF. Plasma is the fluid portion of blood (i.e., whole blood minus the so-called formed elements red cells, white cells, and platelets).

The fluid in the intravascular compartment is the fluid that is present in all of body blood vessels. These two compartments are separated by the capillary endothelium (lining of the walls of the capillaries).

The extracellular fluid (ECF) compartment is further subdivided into the intravascular compartment and the extravascular compartment. Approximately 33% of the total body fluid (or ~20% of total body weight) is in the extracellular fluid (ECF) compartment. The intracellular fluid is separated from the extracellular fluid by the cell plasma membrane. Therefore, the total volume of ICF is ~28 L (cytoplasmic volume of all cells combined). Approximately 67% of total body water (or ~40% of total body weight) is in the intracellular fluid (ICF) compartment, which is the fluid that is present in the cytoplasm of all cells of the body. If we use 70 kg (155 lb) to represent the average adult male, the total volume of water in the body can be calculated to be about 42 L. In a typical adult male human, approximately 60% of the total body weight is composed of water.

Body fluid compartments transcellular