It is a long and cylindrical muscle. Its length is 1-4 cm and diameter is 10-40 micrometers. It is also called muscle fiber because the cells look like fine fibers.
1. Sarcolemma: Muscle tissue is covered by a sheath called sarcolemma.
2. Sarcoplasm: Its cytoplasm is called sarcoplasm. Cytoplasm contains mitochondria. Because these cells require a lot of energy.
3. Nucleus: Multiple nuclei in each muscle cell. It performs biological functions of cells.
4. Myofibril: Myofibril fibers are present along the length of the cell. Myofibril fibers are composed of actin and myosin filaments. Actin and myosin filaments together are called sarcomere. Myofibrils have two types of lines or bands. anisotropic band (A) and isotropic band (I). Darker bands are called anisotropic or A bands and lighter bands are isotropic or I bands.
5. Transverse lines: Several transverse lines are seen in optional muscles. These lines are called linear muscles or marked muscles.
6. Fasciculus: Muscle fibers are arranged in clusters. Each bundle is called a fasciculus. Each fasciculus is covered by perimycium. Many fasciculi join together to form large clusters. Each large cluster is covered by epimycium.