The Human Body Fluids

The maintenance of a relatively constant volume and a stable composition of the body fluids is essential for homeostasis. Some of the most common and important problems in clinical medicine arise because of abnormalities in the control systems that maintain this relative constancy of the body fluids. The relative constancy of the body fluids is remarkable because there is continuous exchange of fluid and solutes with the external environment, as well as within the different body compartments. For example, fluid intake is highly variable and must be carefully matched by equal output of water from the body to prevent body fluid volumes from increasing or decreasing.