This study represents an effort to tabulate the normal mean cross-sectional diameters of human striated muscle fibers in post-mortem material ranging in age from five months gestation through senescence. Age, sex, height and weight of the subjects were taken into account. Cases with neuromuscular illnesses or inanition were specifically excluded. All measurements represent mean narrow fiber diameter of celloidin embedded material sampled at the maximum diameter of the muscle belly. Noteworthy findings include a rapid increase in mean narrow diameter of all muscles except gastrocnemius from gestation to the immediate neonatal period. This was followed by a slower gradual increase in fiber diameter until the age of puberty when again a rapid increase was noted in all muscles except the superior rectus. Following puberty, the superior rectus diameter remained relatively constant throughout life. The sternomastoid, deltoid, biceps, sartorius, quadriceps and gastrocnemius continued a gradual steady increase in fiber size until the late third to early fourth decade, thereafter slowly diminishing in size by the ninth decade. Data are presented to show that the fusiform shape of the biceps muscle cannot be entirely attributed to the fusiform shape of the individual fibers. Particular care must be taken in selecting the level of measurement as fiber diameters appear to be significantly larger near the maximum breadth of the muscle bely. Factors are presented for conversion of measurements between various methods of histologic processing. A useful rule is that the ratio of the sizes of fresh-frozen, fixed-frozen, celloidin and paraffin embedded fibers is roughly 10:9:8:7.
Human Skeletal Muscle Autopsy Material Biometric Analysis Fiber Diameter Histograms