Explain the structure of a skeletal muscle fibre.

Explanation

Each muscle fibre is thin and elongated. It has multiple oval nuclei beneath sarcolemma. The cytoplasm of the muscle fibre is called as sarcoplasm. It contains glycosomes, the stored glycogen granules, myoglobin, respiratory pigment and sarcoplasmic reticulum. Actin and myosin are muscle proteins present in the muscle fibre. Each myofibril has a repeated series of dark and light bands called A-bands and l-bands. Each dark band has a lighter region in its middle called the H-zone. Each H-zone is bisected vertically by a dark line called the M-line. Each light I-band has a darker mid line area called the Z-disc.
Sarcomere is the functional unit of the skeletal muscle. It is a region of a myofibril between two successive Z-discs.
Sarcomere has thick and thin filaments. The thick filaments extend the entire length of the A-band, the thin filaments extend across the I-band and partly into the A-band.
The invagination of the sarcolemma forms transverse tubules (T-tubules) and they penetrate into the junction between the A and I-bands.