Normal value of arterial HC03′ in gas exchange is
**Core Concept**
Arterial bicarbonate (HCO3-) is a crucial component of the bicarbonate buffering system, which plays a vital role in maintaining acid-base balance in the body. The normal value of arterial HCO3- is a reflection of the body's ability to regulate pH levels through this buffering system.
**Why the Correct Answer is Right**
The normal value of arterial HCO3- is around 22-28 mmol/L. This range is maintained through the action of the kidneys, which excrete excess HCO3- in the urine and reabsorb it when necessary. The bicarbonate buffering system works in conjunction with the respiratory system, which regulates the concentration of carbon dioxide (CO2) in the blood. When CO2 levels increase, the blood becomes more acidic, and the kidneys respond by increasing HCO3- reabsorption, which helps to buffer the excess hydrogen ions. Conversely, when CO2 levels decrease, the kidneys decrease HCO3- reabsorption, allowing the blood to become more acidic.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the normal value of arterial HCO3- is not around 15 mmol/L, which is below the normal range.
**Option B:** This option is incorrect because the normal value of arterial HCO3- is not around 30 mmol/L, which is above the normal range.
**Option D:** This option is incorrect because the normal value of arterial HCO3- is not around 10 mmol/L, which is significantly below the normal range.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that the bicarbonate buffering system is a dynamic process that involves the kidneys, lungs, and other organs working together to maintain acid-base balance. A normal arterial HCO3- value is often a reflection of the body's overall ability to regulate pH levels effectively.
**Correct Answer: C. 24-28 mmol/L**