Abstract
Myofibrous organization was studied in human quadriceps femoris muscles (rectus femoris ; RF, vastus lateralis ; VL, vastus medialis ; VM, vastus intermedius ; VI) in 10 human subjects (5 males and 5 females, ages 44-86 years) . Muscle samples were embedded in celloidin and sections were stained with hematoxylin and eosin. The following results were obtained. 1) Muscle weights and cross-sectional areas were most predominant in VL, followed in order by VM, VI and RF. 2) Number of muscle fiber per sq mm was most predominant in RF (758), followed by VL (562), VM (474) and VI (461) . There was no difference between males and females. 3) VL had the most fibers in cross section, followed by VM, RF and VI. 4) Fiber sizes in VI, VM and VL were about 1300 μm2 and differences among those muscles were small. Fibers in RF (about 1000 μm2) were smaller than those in the other three muscles. Quadriceps femoris muscle had larger muscle fiber size than other human muscles. 5) Density of muscle fibers was highest in RF (71%), and in other muscles were about 60%. The results suggest that VL, which had the largest cross-sectional area and total fiber number, functions most predominantly for knee extention.
