Chapter 42: Gastric Function

The bicarbonate buffer system emerges as the dominant extracellular buffering mechanism, while phosphate and protein buffers provide intracellular and urinary buffering capacity. Respiratory compensation occurs through adjustments in ventilation rates that modulate carbon dioxide elimination, allowing the lungs to rapidly correct acute acid-base disturbances by altering the balance between carbonic acid and bicarbonate. Renal mechanisms provide longer-term regulation through multiple pathways including hydrogen ion secretion in the collecting duct and proximal tubule, bicarbonate reabsorption in the proximal segments, and generation of new bicarbonate through ammonium excretion and titratable acid formation in the urine. The chapter systematically categorizes acid-base disorders into four primary types: respiratory acidosis and alkalosis resulting from ventilatory dysfunction, and metabolic acidosis and alkalosis arising from non-respiratory causes. Clinical conditions including diabetic ketoacidosis, chronic obstructive pulmonary disease, gastric losses through vomiting, and renal insufficiency are analyzed as illustrative examples of how various pathological states disrupt acid-base balance. The chapter demonstrates how these organ systems function in coordinated fashion to maintain homeostasis under health conditions and how compensatory mechanisms operate during disease states, providing essential foundation for understanding critical clinical acid-base disorders.