ANATOMY

Detailed explanation-1: -Total body potassium is approximately 55 mEq/kg body weight. Of this amount, 98% is in the intracellular compartment (primarily in the muscle, skin, subcutaneous tissue, and red blood cells) and 2% is in the extracellular compartment.

Detailed explanation-2: -The total body potassium content is dependent on sex, age, and, most importantly, muscle mass (which contains 60–75% of total body potassium), and is approximately 40–45, and 50–55 mmol per kilogram of body weight for normal adult women and men, respectively.

Detailed explanation-3: -Potassium is the primary intracellular cation; 95-98% of the total body potassium is found in the intracellular space, primarily in muscle. Total body potassium stores amount to approximately 50 mEq/kg (3500 mEq in a 70-kg person).

Detailed explanation-4: -The concentration of potassium in the extracellular fluid is a critical determinant of the resting membrane potential of cells and must be maintained within a narrow range, normally between 3.5 and 5 mM in plasma concentration.