Explain briefly the term 'sarcomere'.

Explanation

**Step-by-Step Solution:**

1. **Definition of Sarcomere**: A sarcomere is the basic structural and functional unit of striated muscle tissue. It is the smallest contractile unit within a muscle fiber.

2. **Structure of Sarcomere**: Sarcomeres are composed of thick and thin filaments. The thick filaments are primarily made of myosin, while the thin filaments are primarily made of actin, along with regulatory proteins such as troponin and tropomyosin.

3. **Arrangement of Sarcomeres**: Sarcomeres are arranged end to end along the length of a myofibril, which is a long, cylindrical structure that runs parallel to the muscle fiber. This arrangement gives skeletal muscle its striated appearance.

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