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Schwann cells begin to form myelin sheat...

Schwann cells begin to form myelin sheaths around axons :

A

When neurons are injured

B

During fetal develeopment

C

After birth

D

Only in response to a disorder

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The correct Answer is:
**Step-by-Step Solution:** 1. **Understanding Schwann Cells**: Schwann cells are a type of glial cell found in the peripheral nervous system. Their primary role is to form the myelin sheath around the axons of neurons. 2. **Identifying the Options**: The question presents four options regarding when Schwann cells begin to form myelin sheaths around axons: - Option 1: When neurons are injured - Option 2: During fetal development - Option 3: After birth - Option 4: Only in response to a disorder 3. **Evaluating Each Option**: - **Option 1**: When neurons are injured - This is incorrect. Schwann cells can assist in regeneration after injury, but myelination does not begin at this stage. - **Option 2**: During fetal development - This is correct. Myelination begins during fetal development, as Schwann cells wrap around the axons of developing neurons. - **Option 3**: After birth - This is incorrect. While myelination continues after birth, the initial formation begins during fetal development. - **Option 4**: Only in response to a disorder - This is incorrect. Myelination is a normal developmental process, not solely a response to disorders. 4. **Conclusion**: The correct answer is **Option 2: During fetal development**. This is when Schwann cells start to form myelin sheaths around axons.
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