Osmolæritet

Osmolæritet, also spelled osmolality, is a measure of the total concentration of osmotically active particles in a solution. It is expressed in units of osmoles per kilogram of solvent (osmol/kg). Osmolæritet is a critical concept in physiology, biochemistry, and pharmacology, as it determines the movement of water across cell membranes and the overall balance of fluids in the body.

The primary osmotically active particles in biological systems are electrolytes, such as sodium (Na+), potassium (K+), and chloride (Cl-), as well as nonelectrolytes like glucose and urea. Each of these particles contributes to the osmolæritet of a solution. For example, a solution containing 150 mmol/L of sodium chloride (NaCl) has an osmolæritet of approximately 300 osmol/kg, as each mole of NaCl dissociates into two osmotically active particles.

Osmolæritet is essential for maintaining homeostasis in the body. For instance, the osmolæritet of extracellular fluid (ECF) is tightly regulated to ensure proper hydration and cellular function. Abnormal osmolæritet can lead to conditions such as dehydration, hyponatremia, or hypernatremia, which can have serious consequences for health.

In clinical settings, osmolæritet is measured using specialized instruments, such as osmometers, which determine the freezing point depression or vapor pressure of a solution. This information is crucial for diagnosing and managing conditions related to fluid and electrolyte balance.