What is the major cation in extracellular fluid (ECF)?

Sodium is recognized as the major cation in extracellular fluid (ECF) due to its significant role in maintaining fluid balance and creating osmotic pressure in the body. ECF is primarily composed of plasma and interstitial fluid, where sodium ions are abundant. The high concentration of sodium in the ECF is critical for several physiological functions, including the regulation of blood volume, blood pressure, and the transmission of nerve impulses.

Sodium’s prominence in ECF contrasts with potassium, which is the principal cation found in intracellular fluid (ICF). Magnesium and calcium also play vital roles in various bodily functions but are present in much lower concentrations in the ECF compared to sodium. Thus, the focus on sodium underscores its essential contribution to maintaining homeostasis and overall fluid balance within the body.