Electron micrograph of skeletal muscle fiber. This low-magnification electron micrograph shows the general organization of skeletal muscle fibers. Small portions of three muscle fibers in longitudinal profile are included in this micrograph. The muscle fiber on the right reveals a nucleus at its periphery. Two fibers-one in the middle and another on the left-exhibit regular profiles of myofibrils separated by a thin layer of surrounding sarcoplasm (Sr). Each repeating part of the myo fibril between adjacent Z lines is a sarcomere (S). The cross-banded pattern visible on this micrograph reflects the arrangement, in register, of the individual myofibrils (M); a similar pattern found in the myofibril reflects the arrangement of myofilaments. The detailed features of a sarcomere are shown at higher magnification in Figure 10.6a. The presence of the connective tissue in the extracellular space between the fibers constitutes the endomysium of the muscle, x6,500.
thin filament thick filament thin filament thick filament
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