Though similar to molarity, osmolarity refers to the total number of active particles. One osmole refers to one mole of osmotically active solute particles. The unit of osmoles is used to express the number of particles. The tendency of a solution to draw water in through the semipermeable membrane is the osmotic pressure.

The solute concentration difference across the membrane gives rise to a gradient that facilitates the movement of a solvent (usually water in our body) until attaining equilibrium. In the human body, this selectively permeable membrane may be the cellular membrane (in the case of intracellular fluid) or maybe a membrane lining your body cavity composed of cells (in the case of extravascular fluid). Osmosis occurs when two solutions containing different concentrations of solute are divided by a selectively permeable membrane. This article will provide an overview of osmoregulation and excretion, focusing on a discussion of the renal system involved in maintaining this intimate balance between fluid retention and excretion.

This process of passive regulation of osmotic pressure is known as osmoregulation. The maintenance of fluid homeostasis in each of these compartments is dependent on the excretion of fluids and the concentration of electrolytes that generate osmotic pressure. The intracellular fluid makes up roughly two-thirds of the total body volume.Įxtracellular fluid constitutes the remaining one-third of fluid volume in the body and may further divide into its interstitial, intravascular and transcellular compartments. Intracellular fluid, also considered as the cytosol, is all the fluid contained within cells. Our body fluids may subcategorize into intracellular and extracellular fluid compartments. The average adult has roughly 65% fluid mass, with this value being slightly lower in females than males. As living organisms, the maintenance of fluid balance is critical to sustaining many bodily functions, including metabolic and biochemical reactions, transport of nutrients and thermoregulation.

Body fluid compartments