Cytology of Muscle and Neuromuscular Junction
1983; Elsevier BV; Linguagem: Inglês
10.1016/b978-0-12-751404-8.50009-8
AutoresGhislain Nicaise, J. Amsellem,
Tópico(s)Planarian Biology and Electrostimulation
ResumoThis chapter presents the cytology of muscle and neuromuscular junction. The classifications of molluscan muscle cells into cross-striated, obliquely striated, and smooth muscles, with subclasses, are based on their appearance in living cells under light microscopy. The striation is a crucial morphological feature. However, the exceptional diversity of molluscan muscles cannot be expressed by a single gradient in which structure and function are seen to evolve from the genuine fast, cross-striated cell to the slow, smooth type. Studies on the cytology of muscle represents a selection of molluscan muscles in which every cell type differs from the others in at least one of the following parameters: organization of the Z elements (Z), length of the thick filaments (L), main diameter of the thick filaments (F), plasma membrane invaginations (T), sarcoplasmic reticulum (R), and relative abundance of mitochondria (M). Relevant information could be obtained from the thin/thick filament ratio, which appears to be proportional to the thick filament diameter. Other morphological attributes such as the development of extracellular spaces and glio-interstitial tissue are still less well documented. The intercellular cleft is of constant width in the nerve-muscle junctional region; its dimensions vary from 10 to 30 nm depending on the species and perhaps also on the neurotransmitter (two different nerve endings on the same muscle cell may have different cleft widths). The junctional region is further characterized by an electron dense, amorphous lamina in the middle of the cleft and by the presence of synaptic vesicles in the nerve ending.
Referência(s)