05.3 Acid-base balance

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary consequence of uncontrolled acidosis on cellular functions?

Increased bicarbonate production

Decreased potassium secretion

Enhanced renal bicarbonate handling

Impaired cellular functions (correct)

Which mechanism reduces tubular pH to 4.5 in the late distal and collecting tubules?

Carbonic anhydrase activity increase

H⁺-K⁺ ATPase secretion (correct)

Na⁺-H⁺ counter-transport

Bicarbonate reabsorption enhancement

Which medication class primarily influences acid-base balance through alterations in Na⁺ and K⁺ levels?

Diuretics (correct)

Beta-blockers

ACE inhibitors

Calcium channel blockers

What is a key physiological response to manage acidosis concerning bicarbonate production?

Excess H⁺ combining with buffer systems Signup and view all the answers

How is anion gap calculated, and what does it indicate?

[Na⁺] - ([Cl⁻] + [HCO₃⁻]); indicates acid-base disturbance Signup and view all the answers

What characterizes metabolic alkalosis in terms of bicarbonate levels?

Primary increase in HCO₃⁻ Signup and view all the answers

Which type of acidosis is identified by a high anion gap?

Metabolic acidosis Signup and view all the answers

What is a crucial distinguishing factor between metabolic and respiratory causes of acid-base disturbances?

The interpretation of arterial blood gas measurements Signup and view all the answers

How do the kidneys primarily manage extracellular pH?

By secreting hydrogen ions and reabsorbing bicarbonate Signup and view all the answers

What mechanism allows bicarbonate reabsorption in the kidneys?

HCO₃⁻ combines with secreted H⁺ to form H₂CO₃ Signup and view all the answers

Which buffer system is particularly effective in tubular fluid for correcting acidosis?

Phosphate buffer system Signup and view all the answers

During metabolic acidosis, how does the kidney compensate?

By increased hydrogen ion excretion Signup and view all the answers

What is the role of ammonia in renal acid-base balance?

To buffer hydrogen ions during acidosis Signup and view all the answers

What clinical assessment is vital for differentiating acid-base disturbances?

Assess ABG values including pH and anion gap Signup and view all the answers

In which situation might you expect to see increased hydrogen ion excretion?

Metabolic acidosis from gastrointestinal loss Signup and view all the answers

Which of these statements about acidic and basic urine is true?

Acidic urine decreases extracellular base by secreting hydrogen ions Signup and view all the answers

Study Notes

Acid-Base Balance: Renal Control

The kidneys regulate extracellular pH by excreting either acidic or basic urine.
This process involves hydrogen ion secretion, bicarbonate reabsorption, and bicarbonate generation.
Acidic urine decreases extracellular acid, while basic urine removes base.

Renal Hydrogen Ion Secretion

Occurs in the renal tubules via counter-transport with sodium.
Carbon dioxide (CO2) and water (H2O) form carbonic acid (H2CO3), which dissociates into hydrogen ions (H+) and bicarbonate ions (HCO3-).

Bicarbonate Reabsorption

Filtered bicarbonate combines with secreted hydrogen ions to form carbonic acid (H2CO3).
Carbonic acid dissociates into carbon dioxide (CO2) and water (H2O), enabling bicarbonate reabsorption.

Renal Bicarbonate Production

Newly generated bicarbonate compensates for losses or increases.

Phosphate Buffer System

Phosphate buffers hydrogen ions (H+), particularly effective in tubular fluid due to concentration.

Ammonia Buffer System

Ammonia (NH3) and ammonium ions (NH4+) derived from glutamine act as buffers for hydrogen ions, crucial in acidosis.

Clinical Applications

Metabolic acidosis (e.g., diarrhea) can lead to low bicarbonate levels, prompting the kidneys to increase hydrogen excretion.
ABGs (arterial blood gases) help diagnose metabolic and respiratory acid-base imbalances.
Treatment of metabolic acidosis involves bicarbonate reabsorption; respiratory acidosis involves compensatory adjustments in plasma bicarbonate.

Pathophysiology

Early tubular segments (proximal tubule, thick ascending limb, early distal tubule) secrete hydrogen ions from carbon dioxide.
CO2 diffuses into cells, forming carbonic acid (H2CO3), which then dissociates into hydrogen ions and bicarbonate.
Hydrogen ions are secreted via sodium-hydrogen counter-transport (Na-H counter-transport).

Pharmacology

Diuretics influence acid-base balance by altering sodium and potassium levels.
ACE inhibitors and ARBs decrease angiotensin II, reducing sodium reabsorption, indirectly influencing hydrogen and bicarbonate handling.

Differential Diagnosis

Metabolic acidosis is categorized based on anion gap.
Respiratory acidosis results from hypoventilation, while metabolic alkalosis results from primary increase in bicarbonate (e.g., vomiting, diuretic use).
Respiratory alkalosis occurs due to hyperventilation.

Investigations

Arterial blood gases (ABGs) measure pH, pCO2, HCO3, pO2, and anion gap.
Anion gap calculation is used to determine metabolic derangements.

Summary and Key Takeaways

Kidneys maintain pH balance by controlling hydrogen ion secretion and bicarbonate reabsorption.
Phosphate and ammonia buffer systems are vital in managing excess hydrogen ions, particularly in acidosis.
Distinguishing metabolic from respiratory acid-base causes is essential for proper diagnosis and treatment.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz explores the renal mechanisms involved in maintaining acid-base balance in the body. Key processes such as hydrogen ion secretion and bicarbonate reabsorption are examined in detail. Test your understanding of how the kidneys regulate extracellular pH through urine composition.