How does the body maintain blood pH within normal limits?

• A. Through the liver's metabolic activities.
• B. Through buffers in the blood and organ functions.
• C. Through muscle contractions.
• D. Through hormone secretions from glands.

Answer: (B)

The body maintains blood pH within normal limits primarily through the action of buffers in the blood and the functions of various organs. Buffers, such as bicarbonate, proteins, and phosphates, help to neutralize acids and bases in the blood, thereby stabilizing pH levels. When there is an increase in acidity (lower pH), bicarbonate can react with hydrogen ions to reduce acidity, helping to return the pH to a normal range. Conversely, if the blood becomes too alkaline (higher pH), the buffer system can release hydrogen ions, making the blood more acidic.

In addition to the immediate effects of buffering, the kidneys and lungs play critical roles in longer-term pH regulation. The kidneys can excrete excess acids or bases, while the lungs regulate the carbon dioxide levels by adjusting the rate of respiration, as carbon dioxide in the blood can affect pH levels. Together, these mechanisms ensure that blood pH remains tightly regulated, typically around 7.35 to 7.45, which is vital for proper cellular functions.

Other options, while they may contribute to overall homeostasis in the body, do not directly address the maintenance of blood pH in the same immediate and effective manner as the buffering system and