Fine structure of fiber types in normal human muscle

Abstract

Abstract The fine structure of fiber types in the human vastus lateralis muscle is described. In contrast to the types in other mammals, the two types (red and white) in this muscle seem to differ only in the number and size of mitochondria and not in the amount of sarcoplasmic reticulum or in the structure of myofibrils. The continuity of fiber plasma membrane with the T tubules in the fiber is described. Occasional degenerate foci, which have been found in the normal muscle, are also described.