Final answer:
The striated appearance of skeletal muscle cells is due to the alignment of sarcomeres composed of actin and myosin proteins, which form repeating dark and light bands within the myofibrils of the muscle.
Step-by-step explanation:
The striated appearance of skeletal muscle tissue is due to the parallel bundles of myofibrils within the muscle cells. These myofibrils contain repeating units called sarcomeres, which are made up of myofilaments of the proteins actin and myosin. These proteins are arranged in a regular pattern that causes light and dark bands when viewed under a microscope, contributing to the striated look of the muscle. The sarcomeres are lined up end to end along the myofibril, and it is the alignment of these sarcomeres that causes the entire muscle fiber to appear striated.
These muscle fibers are multinucleated due to the fusion of myoblasts during their development and are surrounded by connective tissue. Skeletal muscles are responsible for voluntary movements under the control of the somatic nervous system, and they contrast with non-striated smooth muscle tissue.