The key solutes in the extracellular fluid include:
1. Sodium (Na+): The most abundant extracellular cation, crucial for maintaining osmotic balance and membrane potential. 2. Potassium (K+): Though primarily intracellular, its concentration in the ECF is vital for nerve and muscle function. 3. Calcium (Ca2+): Important for muscle contraction, neurotransmitter release, and blood clotting. 4. Chloride (Cl-): The primary extracellular anion, essential for maintaining osmotic balance and electrical neutrality. 5. Bicarbonate (HCO3-): A key component of the body's buffering system, helping to maintain pH balance. 6. Proteins: Although present in lower concentrations compared to intracellular fluid, extracellular proteins like albumin play roles in maintaining osmotic pressure and transporting substances.
