What is the primary buffer system in the extracellular fluid?

The primary buffer system in the extracellular fluid is the bicarbonate buffer system. This is due to its effectiveness in maintaining the pH of blood and other extracellular fluids within a narrow and optimal range, which is crucial for physiological functions.

The bicarbonate buffer system operates through a reversible reaction involving carbonic acid (H2CO3) and bicarbonate ions (HCO3-). When the pH of the blood decreases (becomes more acidic), bicarbonate ions can react with excess hydrogen ions (H+) to form carbonic acid, thereby reducing acidity. Conversely, if there is an increase in pH (becoming more alkaline), carbonic acid can dissociate to release hydrogen ions and bicarbonate, helping to restore balance.

While other buffer systems, such as the protein buffer system, phosphate buffer system, and hemoglobin buffer system, also play roles in buffering, their primary functions differ based on their locations and mechanisms. For instance, the protein buffer system is more significant in intracellular fluid and has a role in buffering proteins rather than being the primary extracellular buffer. The phosphate buffer system operates mainly in the intracellular fluid and is less significant in terms of blood pH regulation. The hemoglobin buffer system mainly functions in the red blood cells and is