Concentration of sodium and chloride ions is lowest

Options

A. Near the cortex
B. Deep in medulla
C. In the interstitial fluid
D. In the middle of Henle's loop

Answer

To determine where the concentration of sodium and chloride ions is lowest in the kidney, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Structure of the Kidney**:
- The kidney is divided into two main regions: the cortex and the medulla. Each of these regions has distinct functions related to the filtration and regulation of blood.

2. **Identify the Functional Unit**:
- The nephron is the functional unit of the kidney. It is responsible for filtering blood, reabsorbing essential substances, and excreting waste products.

3. **Role of Sodium and Chloride Ions**:
- Sodium (Na+) and chloride (Cl-) ions are crucial for various physiological processes. The kidneys regulate their concentration through processes of filtration, reabsorption, and secretion.

4. **Location of Lowest Concentration**:
- In the kidney, the concentration of sodium and chloride ions is lowest in the cortex. This is because, during the filtration process, most of the sodium and chloride ions are reabsorbed in the nephron, particularly in the proximal convoluted tubule and loop of Henle, which are located in the medulla.

5. **Conclusion**:
- Therefore, the concentration of sodium and chloride ions is lowest in the renal cortex of the kidney.

### Final Answer:
The concentration of sodium and chloride ions is lowest in the renal cortex of the kidney.

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