Chapter 28: Acid-Base Physiology

The body generates acid continuously through metabolic processes, and the chapter explains how the respiratory and renal systems work together to eliminate or retain hydrogen ions and bicarbonate to preserve acid-base balance. The discussion begins with fundamental concepts including the definition of acids and bases, the Henderson-Hasselbalch equation, and how buffer systems function to resist pH changes. The three primary buffering systems in the body are presented: the bicarbonate buffer system, which operates in both blood and tissues and represents the most important defense against pH fluctuation; the phosphate buffer system, which contributes significantly in intracellular compartments; and the protein buffer system, including hemoglobin's critical role in buffering carbonic acid. The respiratory system provides rapid compensation by adjusting ventilation to increase or decrease carbon dioxide elimination, thereby controlling the volatile acid component of blood. The kidneys offer slower but more powerful long-term regulation by controlling bicarbonate reabsorption and hydrogen ion secretion, allowing for sustained correction of acid-base disturbances. The chapter distinguishes between metabolic and respiratory acidosis and alkalosis, explaining the pathophysiological mechanisms underlying each condition and how the body generates appropriate compensatory responses. Clinical correlations address diabetic ketoacidosis, hyperventilation, renal failure, and other disorders that disrupt acid-base homeostasis. By integrating respiratory physiology, renal function, and cellular metabolism, this chapter demonstrates how the body maintains the precise pH environment necessary for enzyme function, cellular signaling, and overall physiological stability.