The control of blood pH by the kidneys during acidosis involves
(a) The secretion of hydrogen ions and reabsorption of bicarbonate ions from the tubular fluid
(b) A decrease in the amount of water reabsorbed
(c) Hydrogen ion reabsorption and bicarbonate ion loss
(d) Potassium ion secretion

Verified step by step guidance

Understand the role of the kidneys in maintaining blood pH, especially during acidosis, which is a condition where blood pH drops below normal (becomes more acidic).

Recall that the kidneys help correct acidosis primarily by removing excess hydrogen ions (H\_+) from the blood and conserving bicarbonate ions (HCO\_3\^-) which act as a buffer to neutralize acid.

Analyze each option: (a) mentions secretion of hydrogen ions and reabsorption of bicarbonate ions, which aligns with the kidney's mechanism to raise blood pH during acidosis.

Option (b) suggests a decrease in water reabsorption, which is not directly related to pH control; (c) suggests hydrogen ion reabsorption and bicarbonate loss, which would worsen acidosis; (d) involves potassium ion secretion, which is more related to electrolyte balance than direct pH control.

Conclude that the correct physiological response during acidosis is the secretion of hydrogen ions into the tubular fluid and reabsorption of bicarbonate ions back into the blood, as described in option (a).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Renal Regulation of Blood pH

The kidneys maintain blood pH by adjusting the excretion or reabsorption of hydrogen ions (H⁺) and bicarbonate ions (HCO₃⁻). During acidosis, kidneys increase H⁺ secretion into the tubular fluid and reabsorb more bicarbonate to neutralize excess acid and restore pH balance.

Hydrogen Ion Secretion Mechanism

Hydrogen ions are secreted by renal tubular cells into the urine primarily via active transport mechanisms. This process removes excess acid from the blood, helping to correct acidosis by lowering H⁺ concentration in the bloodstream.

Bicarbonate Reabsorption in the Kidneys

Bicarbonate ions are reabsorbed in the renal tubules to conserve base and buffer blood pH. Increased reabsorption during acidosis helps neutralize excess hydrogen ions, preventing blood from becoming too acidic.

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