The area between two Z lines is called a …………....

Explanation

**Step-by-Step Solution:**

1. **Identify the Z Lines**: The Z lines are structures found in striated muscle fibers that serve as boundaries for the contractile units of the muscle.

2. **Understand the Structure of Myofibrils**: Myofibrils are the long, thread-like structures within muscle cells that are responsible for muscle contraction. They are made up of repeating units.

3. **Define the Contractile Unit**: The area between two Z lines is referred to as a contractile unit. This unit is crucial for muscle contraction.

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