Skeletal muscle cells, also known as muscle fibers, are long, cylindrical cells that make up the skeletal muscles in the body. These cells are multinucleated, meaning they contain multiple nuclei, which helps them manage the high demand for energy and protein synthesis during muscle contraction. They are striated, giving them a striped appearance under a microscope, and are responsible for voluntary movements, such as walking and lifting. Skeletal muscle cells are activated by signals from the nervous system, allowing them to contract and produce force. They rely on energy sources like ATP and can adapt to different types of physical activity, becoming stronger and more efficient with regular exercise.