The Schwann sheath is :

Options

A. A non myelinated nerve fibres
B. Associated with myelin sheath
C. A connective tissue cell
D. Associated with myelinated & non myelinated nerve fibre

Answer

**Step-by-Step Solution:**

1. **Understanding Schwann Sheath**: The Schwann sheath, also known as the neurilemma, is a protective covering that surrounds the axons of neurons in the peripheral nervous system. It is formed by Schwann cells.

2. **Function of Schwann Sheath**: The primary function of the Schwann sheath is to insulate the axon and facilitate the conduction of nerve impulses. It can be associated with both myelinated and non-myelinated nerve fibers.

3. **Analyzing the Options**:
- **Option 1: Non-myelinated nerve fiber**: This option is incorrect because while Schwann cells do surround non-myelinated fibers, the Schwann sheath is not exclusively associated with them.
- **Option 2: Myelin sheath**: This option is also incorrect. The myelin sheath is specifically associated with myelinated nerve fibers, which are formed by multiple layers of Schwann cell membranes.
- **Option 3: Connective tissue shell**: This option is incorrect as well. The Schwann sheath is not merely a connective tissue shell; it has specific functions related to nerve fibers.
- **Option 4: Associated with myelinated and non-myelinated nerve fibers**: This option is correct. The Schwann sheath is indeed associated with both types of nerve fibers.

4. **Conclusion**: The correct answer to the question "The Schwann sheath is:" is that it is associated with both myelinated and non-myelinated nerve fibers.

**Final Answer**: The Schwann sheath is associated with myelinated and non-myelinated nerve fibers.

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