Which endocrine gland is not Ectodermal in origin?

Options

A. Pineal body
B. Anterior pituitary
C. Adrenal medulla
D. Thymus

Answer

To determine which endocrine gland is not ectodermal in origin, we need to analyze the origins of the listed glands: Pineal body, Anterior pituitary, Adrenal medulla, and Thymus.

### Step-by-Step Solution:

1. **Understand Germ Layers**:
- In triploblastic animals, there are three germ layers: ectoderm, mesoderm, and endoderm.
- Ectoderm gives rise to structures such as the skin and nervous system, while endoderm forms internal organs.

2. **Identify the Glands**:
- **Pineal Body**: This gland is responsible for secreting melatonin and is derived from the ectoderm.
- **Anterior Pituitary**: This gland secretes various hormones (like LH, FSH, growth hormone) and is also derived from the ectoderm.
- **Adrenal Medulla**: This part of the adrenal gland secretes emergency hormones (like adrenaline) and is derived from ectoderm as well.

3. **Examine the Thymus**:
- The thymus gland is crucial for immune function and is responsible for the maturation of T-cells.
- Unlike the other glands mentioned, the thymus originates from the endoderm.

4. **Conclusion**:
- Among the listed options, the thymus gland is the only one that is not ectodermal in origin. Therefore, the correct answer is the **Thymus**.

### Final Answer:
The endocrine gland that is not ectodermal in origin is the **Thymus**.

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