ELECTRON-MICROSCOPE OBSERVATIONS ON HUMAN FETAL STRIATED-MUSCLE

  • 1 January 1978
    • journal article
    • research article
    • Vol. 126  (AUG) , 567-589
Abstract
The superior rectus oculi muscle from human fetuses of 5, 9.2, 10 and 24 cm C-R [crown-rump] length were examined by EM. Myotube satellite cells were present in all specimens but their numbers declined with advancing age: those of active appearance were numerous in the younger specimens but almost absent from the oldest. Active myotube satellites formed an extensive network among the muscle cells and were closely associated with Schwann cells and axons; they may be Schwann cells. Neuromuscular contacts were increasingly numerous with advancing age but seldom occurred on immature muscle cells. The transient polyneuronal innervation seen was reconciled with the scattered distribution of the muscle components of mature motor units.