Final answer:
The plasma membrane of skeletal muscle cells is known as the sarcolemma, which envelopes the sarcoplasm and encompass fibrils forming the sarcomere.
Step-by-step explanation:
The plasma membrane of skeletal muscle cells is called the sarcolemma. A skeletal muscle fiber is surrounded by this plasma membrane, which not only contains the cytoplasm known as sarcoplasm, but also plays a critical role in the muscle cell's function. Within the sarcoplasm, there are many fibrils packaged into orderly units. These fibrils, in their organized structure, form the sarcomere, which is the functional unit of a muscle fiber consisting of contractile proteins such as actin and myosin that give the cell its characteristic striated appearance.