During old age ,the immunity of a person begins to decrease and as a result , the they become more susceptible to infections and diseases . What could be the probable reason for this ?

Options

A. Degeneration of thyroid gland
B. Degeneration of pineal gland
C. Degeneration of thymus gland
D. Degeneration of pituitary gland

Answer

**Step-by-Step Solution:**

1. **Understanding Immunity in Old Age**: The question states that as people age, their immunity decreases, making them more vulnerable to infections and diseases. This is a common observation in geriatric medicine.

2. **Identifying the Role of the Thymus Gland**: The thymus gland is crucial for the development of the immune system, particularly in the maturation of T-lymphocytes (T-cells), which are essential for cell-mediated immunity.

3. **Location and Function of the Thymus**: The thymus gland is located near the heart and is responsible for producing hormones called thymosins. These hormones play a vital role in the maturation and proliferation of T-lymphocytes.

4. **Changes in the Thymus Over Time**: At birth, the thymus is relatively large, but it begins to shrink after birth and continues to do so until puberty, when it becomes significantly smaller. By old age, the thymus may undergo complete degeneration.

5. **Consequences of Thymus Degeneration**: As the thymus degenerates, the production of thymosins decreases. This leads to a reduced proliferation of T-lymphocytes, which in turn weakens the immune response.

6. **Conclusion**: The degeneration of the thymus gland in old age is the primary reason for decreased immunity, making elderly individuals more susceptible to infections and diseases.

**Final Answer**: The probable reason for decreased immunity in old age is the degeneration of the thymus gland, leading to reduced production of thymosins and a decrease in T-lymphocyte proliferation.

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