What is the definition of tonicity in relation to fluids?

Tonicity refers to the physiological effect of a fluid on the volume of cells, which is determined by the concentration of solute particles dissolved in that fluid. It specifically relates to how a solution can affect the movement of water across cell membranes through osmosis. When discussing tonicity, it is crucial to understand that it can be categorized into three types: isotonic, hypertonic, and hypotonic solutions, depending on whether the solute concentration is equal to, greater than, or less than that of the intracellular fluid, respectively.

In clinical contexts, tonicity plays a vital role in intravenous therapy and fluid management—since the choice of fluid can significantly impact cellular hydration and function. Therefore, the definition of tonicity as the concentration of particles dissolved in the fluid is both accurate and essential for understanding fluid dynamics in medical and surgical practices.