Almost all of the sodium ions found in the glomerular filtrate are ______ before urine is excreted.

• A. reabsorbed into the bloodstream
• B. secreted into the collecting duct
• C. converted to potassium ions
• D. excreted unchanged in the urine

Answer: (A)

Verified step by step guidance

1. Understand the function of the glomerulus and the process of filtration: The glomerulus is a network of capillaries in the kidney that filters blood, removing waste products and excess substances to form glomerular filtrate.
2. Learn about sodium ion reabsorption: Sodium ions are crucial for maintaining fluid balance, nerve function, and muscle contraction. The kidneys actively reabsorb most of the sodium ions from the filtrate to prevent excessive loss.
3. Explore the role of the nephron: The nephron, the functional unit of the kidney, reabsorbs sodium ions primarily in the proximal tubule and loop of Henle through active transport mechanisms.
4. Rule out incorrect options: Sodium ions are not converted to potassium ions, nor are they excreted unchanged in the urine. Instead, they are reabsorbed into the bloodstream to maintain homeostasis.
5. Conclude that almost all sodium ions in the glomerular filtrate are reabsorbed into the bloodstream before urine is excreted, ensuring proper electrolyte balance in the body.