Contractile threads present in sarcoplasm of muscle cells are called …………………… .

Explanation

**Step-by-Step Solution:**

1. **Identify the Structure**: The question asks about the contractile threads present in the sarcoplasm of muscle cells.

2. **Define the Term**: These contractile threads are known as **myofibrils**.

3. **Understand the Composition**: Myofibrils are composed of smaller units called **sarcomeres**, which are the basic functional units of muscle contraction.

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