Describe in detail, the structure of skeletal muscle fibre.
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Structure:
1. They consist of large number of fasciculi which are wrapped by a connective tissue sheath called epimysium or fascia. Each individual fasciculus covered by perimysium.
2. Each fasciculus in turn consists of many muscle fibres called myofibers.
3. Each muscle fibre is a syncytial fibre that contains several nuclei.
4. The sarcoplasm (cytoplasm) is surrounded by the sarcolemma (cell membrane).
5. The sarcoplasm contains large number of parallelly arranged myofibrils and hence the nuclei gets shifted to the periphery.
6. Each myofibril is made up of repeated functional units called sarcomeres.
7. Each sarcomere has a dark band called anisotropic of ‘A’ band in the centre. ‘A’ bands are made up of the contractile proteins actin and myosin.
8. In the centre of the ‘A’ band is the light area called ‘H’ zone or Hensen’s zone.
9. In the centre of the Hensen’s zone is the ‘M’ line.
10. On either side of the ‘A’ band are light bands called isotropic or ‘I’ bands. These bands contain only actin. Adjacent light bands are separated by the ‘Z’ line (Zwischenscheibe line).
11. The dark and light bands on neighbouring myofibrils correspond with each other to give the muscles a striated appearance.
Functions: Skeletal muscles bring about voluntary movements of the body
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