Final answer:
The body maintains acid-base balance through a buffer system involving the excretion and retention of hydrogen ions and the management of bicarbonate ions by the kidneys and lungs, ensuring a constant pH critical for physiological function.
Step-by-step explanation:
Regulation of Blood pH, Hydrogen Ions, and Bicarbonate
The human body maintains acid-base homeostasis through a robust system involving chemical buffers and physiological mechanisms, particularly the kidneys and lungs. The primary blood buffer system is carbonic acid/hydrogen carbonate. This system functions effectively due to the reversible equation:
CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3-
Excretion and retention of hydrogen ions (H+) as well as the formation or excretion of bicarbonate ions (HCO3-) play pivotal roles in this regulation. The kidneys contribute to this homeostasis by filtering blood and either reabsorbing bicarbonate, excreting H+ or generating new bicarbonate depending on the body's needs.
Through the actions of proton pumps in the collecting ducts and the exchange processes in the proximal convoluted tubules (PCT), the kidneys can perform fine-tuned pH adjustments over several hours.
Conversely, the lungs regulate the levels of carbon dioxide, a component of the buffer system, through respiration. Variations in the rate and depth of breathing can alter the amount of CO2 expelled from the body, having a faster but shorter-lived impact on blood pH.
The interplay between the buffering capacity of blood and the regulatory mechanisms of the kidney and respiratory systems allows the body to maintain a constant pH, which is crucial for proper physiological function.