Which of the following are connected with thymus gland ?

Options

A. It is active in young ones but gradually becomes incnspiciuous after sexual maturity
B. It is is located in the posterior portion of the root of the third ventricle
C. It secretes hormone-thymosin, which promotes immune competence in young T-lymphocycs
D. Both 1 and 3

Answer

To determine which statements are connected with the thymus gland, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Analyze the First Statement**:
- The statement claims that the thymus gland is active in young ones but gradually becomes inconspicuous after sexual maturity.
- **Explanation**: This is true. The thymus gland is indeed most active during childhood and adolescence, playing a crucial role in the development of T-cells, which are essential for the immune response. After puberty, the thymus begins to shrink and becomes less active.

2. **Analyze the Second Statement**:
- The statement claims that the thymus gland is located in the posterior portion of the root of the third ventricle.
- **Explanation**: This statement is false. The thymus gland is located in the thoracic cavity, specifically behind the sternum and between the lungs, not in the brain.

3. **Analyze the Third Statement**:
- The statement claims that the thymus gland secretes the hormone thymosine, which promotes immune competence in young T lymphocytes.
- **Explanation**: This statement is true. The thymus gland produces thymosine, which is critical for the maturation and differentiation of T lymphocytes, enhancing the immune response.

4. **Analyze the Fourth Statement**:
- The statement claims that both the first and third statements are correct.
- **Explanation**: Since both the first and third statements are indeed correct, this statement is also true.

### Conclusion:
Based on the analysis:
- The correct statements regarding the thymus gland are the first and third statements. Therefore, the answer is option 4: both 1st and 3rd statements are connected with the thymus gland.

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