What Produces the Striations of a Skeletal Muscle Cell

Question

What produces the striations of a skeletal muscle cell?
A) the sarcoplasmic reticulum
B) t-tubules
C) sarcoplasm
D) myofilaments

Accepted Answer

The striations of a skeletal muscle cell are produced by the organized arrangement of myofilaments (thin and thick filaments) within the myofibrils. The repeating pattern of light and dark bands seen under a microscope is a result of the overlapping pattern of actin and myosin filaments within the sarcomere, the basic unit of contraction in a muscle cell. The sarcoplasmic reticulum and t-tubules are involved in regulating the release of calcium ions, which is necessary for muscle contraction, but they do not directly produce the striations. The sarcoplasm is the cytoplasm of a muscle cell and does not contribute to the striations.