Urinary excretion of Na is regulated by

Options

A. Anterior pituitary
B. Posterior pituitory
C. Adrenal cortex
D. Adrenal medulla

Answer

**Step-by-Step Solution:**

1. **Understand the Question**: The question asks which gland regulates the urinary excretion of sodium.

2. **Identify Key Hormone**: The primary hormone responsible for sodium regulation in the body is aldosterone. It plays a crucial role in sodium reabsorption.

3. **Locate the Source of Aldosterone**: Aldosterone is secreted by the zona glomerulosa layer of the adrenal cortex.

4. **Explain the Mechanism**: The secretion of aldosterone is stimulated by the Renin-Angiotensin-Aldosterone System (RAAS). When blood volume or osmolarity changes, the kidneys release the enzyme renin.

5. **Describe the RAAS Pathway**: Renin converts angiotensinogen (produced by the liver) into angiotensin I, which is then converted into angiotensin II. Angiotensin II stimulates the adrenal cortex to release aldosterone.

6. **Conclude the Answer**: Since aldosterone is secreted by the adrenal cortex and is responsible for sodium reabsorption, the correct answer to the question is the adrenal cortex.

7. **Eliminate Incorrect Options**:
- **Anterior Pituitary**: Secretes hormones like TSH, FSH, and LH, which are not involved in sodium regulation.
- **Posterior Pituitary**: Secretes oxytocin and ADH, also not involved in sodium regulation.
- **Adrenal Medulla**: Secretes adrenaline and noradrenaline, which do not have a role in sodium regulation.

8. **Final Answer**: The adrenal cortex is the gland that regulates urinary excretion of sodium.

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