Almost all of the sodium ions found in the glomerular filtrate are:

• A. excreted unchanged in the urine
• B. destroyed by renal enzymes
• C. reabsorbed by the renal tubules
• D. converted to potassium ions

Answer: (C)

Verified step by step guidance

1. Understand the role of sodium ions in the kidney: Sodium ions are crucial for maintaining fluid balance, blood pressure, and proper functioning of cells. The kidneys play a key role in regulating sodium levels in the body.
2. Review the process of glomerular filtration: The glomerulus filters blood, allowing water, ions (including sodium), and small molecules to pass into the renal tubules while retaining larger molecules like proteins and blood cells.
3. Learn about tubular reabsorption: After filtration, the renal tubules reabsorb most of the sodium ions back into the bloodstream. This process is essential for maintaining electrolyte balance and preventing excessive loss of sodium in the urine.
4. Understand why sodium ions are not excreted unchanged: If sodium ions were excreted unchanged, the body would lose a significant amount of this vital electrolyte, leading to imbalances and health issues. Instead, the majority are reabsorbed.
5. Clarify why sodium ions are not converted or destroyed: Sodium ions are not converted to potassium ions or destroyed by renal enzymes. Their reabsorption is a selective and active process facilitated by transport proteins in the renal tubules.