Which of the following glands is large sized at birth but reduces in size with ageing ?

Options

A. (a) Pineal gland
B. (b) Pituitary gland
C. (c) Thymus gland
D. (d) Thyroid gland

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks which gland is large at birth but decreases in size with age. This requires knowledge of the functions and size changes of various glands throughout a person's life.

2. **Analyzing the Pineal Gland**: The pineal gland is an endocrine gland that secretes melatonin, which regulates sleep cycles. It remains relatively constant in size throughout life. Therefore, it cannot be the answer.

3. **Analyzing the Pituitary Gland**: The pituitary gland, known as the master gland, regulates various hormones and other endocrine glands. It remains intact and does not decrease in size with age. Thus, it is not the correct answer.

4. **Analyzing the Thymus Gland**: The thymus gland is crucial for the development of T lymphocytes, which are essential for the immune system. It is large at birth but begins to shrink after puberty as it has already produced sufficient T lymphocytes for lifelong immunity. This gland does decrease in size with age, making it a strong candidate for the answer.

5. **Analyzing the Thyroid Gland**: The thyroid gland secretes thyroxine, which is vital for growth and metabolism. It remains functional and intact throughout a person’s life and does not decrease in size. Therefore, it is not the answer.

6. **Conclusion**: Based on the analysis, the gland that is large at birth and reduces in size with aging is the thymus gland.

**Final Answer**: The correct answer is the thymus gland.

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