The contractile unit of muscle is a part of myofibril be- tween

Options

A. Z line and I band
B. Z line and Z line
C. Z line and A band
D. A band and I band

Answer

**Step-by-Step Solution:**

1. **Understanding Muscle Structure**: Begin by recognizing that muscles are soft tissues made up of muscle cells, which contain protein filaments. The two main types of protein filaments in muscle are actin (thin filaments) and myosin (thick filaments).

2. **Identifying Myofibrils**: Myofibrils are the basic rod-like units of a muscle cell. They are composed of repeating units that are essential for muscle contraction.

3. **Defining the Sarcomere**: The sarcomere is defined as the segment of a myofibril that lies between two Z lines (or Z discs). It is the smallest functional unit of muscle contraction.

4. **Components of the Sarcomere**: Within the sarcomere, you will find actin and myosin filaments. The arrangement of these filaments allows for the contraction of the muscle.

5. **Muscle Contraction Mechanism**: During muscle contraction, the sarcomere shortens as the actin filaments slide over the myosin filaments. This sliding mechanism is what causes the muscle to contract.

6. **Final Answer**: Therefore, the contractile unit of muscle, which is the sarcomere, is located between two Z lines in the myofibril.

**Final Answer**: The contractile unit of muscle is a part of myofibril between the two Z lines.

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