1979 年 39 巻 5 号 p. 531-536
The M. rectus abdominis of man was examined, noting the cross-sectional area of venter musculi, the number of muscle fibers per sq. mm., the total number of muscle fibers, the thickness of muscle fibers and the occupational area of muscle fibers in cross-section of the right abdominal rectus specimen of 22 adults. The results obtained were compared with the previously reported pertinent data of the other muscles.
1. The average values (M) of each data of the M. rectus abdominis examined was 205 mm2 in cross-sectional area, 172, 327 in total number of muscle fibers, 1151 μ2 in muscle fiber size and 91% in occupational ratio of muscle fibers.
2. Those muscle specimens which have large cross-sectional area tend to be inferior in number of muscle fibers and to be superior in total number of muscle fibers, size of muscle fibers and occupational ratio of muscle fibers than the specimens which have small cross-sectional area. But the muscle specimens with broader cross-sectional area do not always have a larger size and larger density of muscle fiber while some one of them do contain rich interfibrous connective tissue.
3. As to the relationship of the size of muscle fiber to cross-sectional area of venter musculi, a positive correlation was found to exist, and its of number of muscle fibers per sq. mm. to those showed a tendency of negative correlation.
4. Comparing the myofibrous organization of Rectus abdominis with the other muscles, we found that the cross-sectional area and the total number of this muscle was smaller than that of adductor longus and biceps brachii, and that the size of muscle fibers of this muscle was larger than that of the other muscles except adductor longus.