This chapter describes water as the principal constituent of the human body and is essential for life. In healthy individuals, the volume and osmolality of the tissue fluids are maintained within closely defined limits. This process is mainly concerned with the mechanisms that regulate the quantity of water that is present in the body and maintain its distribution between the different body compartments. The chapter cites some common disorders of electrolyte balance and the detailed mechanisms by which the osmolality of the body fluids is regulated. Broadly speaking, body water is distributed between the intracellular fluid or ICF and the extracellular fluid or ECF.
