Figure 11.

1.4-year Human Denervation. Ultrastructural features of a muscle fiber undergoing atrophy due to lack of innervation. A) The double-layered basal membrane (black and white arrows) argues in favor of these being a regenerated muscle fiber. The fact that the basement membrane itself is folded (Fig. 11A) suggests that this fiber is undergoing atrophy and degeneration due to lack of innervation. B) Within the fiber interior co-exist areas in which the sarcomeric organization of the striated muscle is slightly better preserved (black arrows pointing at the Z lines) and areas presenting clear disarrangement of the contractile elements (dotted oval), more typical of muscle undergoing atrophy/degeneration. C and D) Closer to the fiber periphery, where sarcomeres are better preserved with visible Z and M lines (black and white large arrows) the EC coupling units, normally known as triads (pointed by small black arrows), and the mitochondria (M) are better positioned. On the contrary in areas in which contractile elements are degenerating, the EC coupling system is missing and/or replaced by small vesicles (arrow). Mitochondria may be found clustered, often in proximity of accumulations of glycogen granules (arrowhead).