Abstract
TN his comprehensive review on innerva| tion of skeletal muscle, Tiegs I quotes I statement made by Kuffier ~ that the end plate has become, in recent years, a physiological entity which at present cannot be strictly identified with structure of histologists. One reason: for this hiatus in our knowledge is disagreement which exists among histologists concerning embryologic derivation and limiting boundaries of some of structures which comprise endplate. The controversial points are discussed in detail in Tiegs' review; present description is drawn chiefly from pioneer work of Kiihne ~ and more recent studies of Couteaux 4,5 and Young 6 and their associates. Centrally to its point of contact with muscle fiber, motor axon is ensheathed in a layer of myelin which is closely invested by Schwann cells, The latter are surrounded by a continuous sheath called neurilemma external to which is sheath of Henle, a continuation of perineural sheath surrounding entire bundle of nerve fibers. Near endplate region myelin sheath is lost, and sheath of Henle becomes continuous with outer sarcolemma, an extraneous sheath derived from endomysium. According to Couteaux, 4 at endplate axon retains a surrounding sheath, teloglia, derived from sheath of Schwann, and remains external to true sarcolemma. The latter is modified, beneath axon with its investing teloglia, as pallisade-like subneural apparatus. Whether neurilemma or a derivative is retained is less certain. Surrounding subneural apparatus is a fairly well circumscribed region of granular sarcoplasm which is rich in nuclei. The entire motor endplate occupies a third or less of circumference of muscle fiber. Couteaux has focussed attention on subneural apparatus as probable site of both
Published Version
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