Chapter 18: Problem 10

In what circumstances will the kidneys excrete \(\mathrm{H}^{+}\)ions? What ions will be returned to the blood? How will this affect the \(\mathrm{pH}\) of blood? (p. 426)

Short Answer

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Answer: When blood pH is too low, the kidneys excrete H+ ions, which helps raise the blood pH by reducing its acidity. At the same time, the kidneys reabsorb bicarbonate ions (HCO3-), which enhances the blood's buffer capacity and resists changes in pH levels. This process maintains the blood pH within the optimal range of 7.35-7.45.

Step by step solution

Explain when kidneys excrete H+ ions

The kidneys excrete H+ ions when the blood pH is too low, which indicates acidity. This can happen due to factors like decreased bicarbonate (HCO3-) levels, accumulation of non-volatile acids, or respiratory acidosis. Kidneys help in regulating the acid-base balance in the body by removing excess H+ ions and synthesizing new bicarbonate ions to replace the lost ones.

Describe the process of renal acid excretion

During renal acid excretion, the H+ ions are secreted into the tubular fluid through active transport mechanisms in the proximal tubules, distal tubules, and collecting ducts of the nephron. Simultaneously, bicarbonate ions (HCO3-) are reabsorbed into the blood. H+ ions are primarily excreted through the urine in the form of ammonium ions (NH4+) and titratable acids (such as H2PO4-).

Identify the ions that will be returned to the blood

When kidneys excrete H+ ions, they simultaneously reabsorb bicarbonate ions (HCO3-) from the tubular fluid back into the blood. HCO3- is an essential component of the buffer system in the blood, helping to maintain a stable pH.

Explain how H+ ion excretion affects blood pH

The excretion of H+ ions by the kidneys helps to raise the pH of the blood by removing the excess hydrogen ions, thereby reducing the acidity of the blood. Meanwhile, the reabsorption of bicarbonate ions (HCO3-) enhances the blood's buffer capacity, helping to resist changes in pH levels. These processes work together to maintain the blood pH within the narrow range of 7.35-7.45, ensuring optimal physiological functioning.

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In what circumstances will the kidneys excrete \(\mathrm{H}^{+}\)ions? What ions will be returned to the blood? How will this affect the \(\mathrm{pH}\) of blood? (p. 426)

Short Answer

Step by step solution

Explain when kidneys excrete H+ ions

Describe the process of renal acid excretion

Identify the ions that will be returned to the blood

Explain how H+ ion excretion affects blood pH

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