Figure 1

A schematic drawing of a muscle fiber (muscle cell) in longitudinal- and cross sectional plane. The muscle fiber is surrounded by two membranes, the plasma membr ane (inner) and the basal lamina(outer). The satellite cellsare located between these two membranes, and just beneath the plasma membranelays the myonuclei. The contractile proteins in the muscle cell are arranged in myofibrils. In the longitudinal plane you see that the myofibrilsare organized into sarcomeres separated by the z-disc and the mitochondriaare seen as circular spots between the myofibrils.