What is plasma tonicity?

Plasma tonicity refers to the relative concentration of solutes in the plasma compared to the concentration of solutes in the surrounding tissues. It is a crucial factor in determining the movement of water across cell membranes through osmosis. Tonicity can be classified as isotonic, hypertonic, or hypotonic, depending on whether the plasma has the same, higher, or lower solute concentration than the surrounding fluid. This balance is essential for maintaining cell shape and function in the body.