Question

When examined in cross section at high magnification, skeletal muscle fibers appear stippled because of the presence of numerous myofibrils in the cytoplasm. In longitudinal sections, myofibrils demonstrate cross-striations with alternating regions of light-stained I bands and dark-stained A bands. The precise lateral alignment of light- and dark-stained bands gives skeletal muscle its distinctive striated appearance; hence the term 'striated muscle.' Myofibrils are bundles of the actin and myosin myofilaments that produce muscle fiber contraction. Two types of myofilaments are found in skeletal muscle cells: thick filaments contain myosin, whereas thin filaments contain primarily actin.

Answer 1

The striated appearance of skeletal muscle tissue is due to the orderly arrangement of actin and myosin within the sarcomeres of myofibrils. This creates alternating dark and light bands across muscle cells, which are visible under high magnification and give muscle its characteristic striped look.

Step-by-step explanation:

The striated appearance of skeletal muscle tissue is due to the highly ordered arrangement of myofibrils within the muscle cells. Myofibrils contain repeating units called sarcomeres, which are composed of the contractile proteins actin and myosin. These proteins are arranged into dark A bands and light I bands, which repeat along the myofibrils, giving skeletal muscles their characteristic striated or banded appearance.

Skeletal muscle fibers contain two types of myofilaments essential for muscle contraction. The thick filaments are primarily made up of myosin while the thin filaments contain mainly actin. The precise alignment of these bands within the muscle cell's cytoplasm causes the entire cell, and consequently the whole muscle, to appear striated.

The organization of these proteins differs from the ones found in smooth muscles, which do not show this striated pattern. Observing skeletal muscle fibers at high magnification in both cross section and longitudinal sections reveals the intricacies of these striated patterns, providing insight into the functionality and structural makeup of skeletal muscle tissue.