Trotter J A
Department of Anatomy, University of New Mexico, School of Medicine, Albuquerque 87131.
Acta Anat (Basel). 1993;146(4):205-22. doi: 10.1159/000147459.
The work done by the contractile proteins of muscle in accelerating, decelerating, or maintaining the positions of skeletal elements requires the efficient transmission of tension across the surface membranes of the fibers. The most widely studied sites of tension transmission are the ends of muscle fibers where they contact either connective or epithelial tissues. In most animals, regardless of phylum, muscle fiber ends are characteristically folded, producing a junctional interface that significantly reduces the absolute value of stress applied to the cell membrane, insures that the principle stress vector at the cell membrane is shear rather than tension, and minimizes stress concentrations. The morphological and molecular similarities of muscle-tendon junctions (MTJs) in different animals suggest that the problem of creating a strong adhesive joint between a muscle fiber and a tissue of dissimilar physical properties is essentially the same for all muscles, and that the solution arose early in evolution. In addition to those muscle fiber ends that occur where fibers contact dissimilar tissues, there are intramuscular fiber terminations that consist either of folded cell-cell junctions similar to the fasciae adherentes of cardiac muscle, or of gradually tapering fiber ends. Both sorts of intramuscular ends occur in those vertebrate muscles in which the individual muscle fibers are too short to reach from the tendon of origin to the tendon of insertion. In series-fibered muscles in which the fiber ends are tapered, tension is transmitted from contractile proteins to endomysial collagen fibrils across the fiber membranes. The endomysium of such muscles is an essential series-elastic element. The existing evidence suggests that tension transmission is a general property of muscle cell surfaces, and that specific junctional morphologies are the results of dynamic interactions between muscle cells and the tissues to which they adhere.
肌肉收缩蛋白在加速、减速或维持骨骼元件位置时所做的工作，需要张力在纤维表面膜上有效传递。研究最广泛的张力传递部位是肌肉纤维与结缔组织或上皮组织接触的末端。在大多数动物中，无论所属门类如何，肌肉纤维末端的特征都是折叠的，形成一个连接界面，该界面显著降低了施加到细胞膜上的应力绝对值，确保细胞膜上的主应力矢量是剪切力而非张力，并使应力集中最小化。不同动物中肌腱连接（MTJ）的形态和分子相似性表明，在肌肉纤维与物理性质不同的组织之间形成牢固粘附连接的问题，对所有肌肉来说本质上是相同的，而且这个解决方案在进化早期就出现了。除了纤维与不同组织接触处的那些肌肉纤维末端外，还有肌内纤维末端，它们要么由类似于心肌闰盘的折叠细胞间连接组成，要么由逐渐变细的纤维末端组成。这两种肌内末端都出现在那些单个肌肉纤维太短而无法从起始肌腱延伸到插入肌腱的脊椎动物肌肉中。在纤维末端呈锥形的串联纤维肌肉中，张力从收缩蛋白通过纤维膜传递到肌内膜胶原纤维。这种肌肉的肌内膜是一个重要的串联弹性元件。现有证据表明，张力传递是肌肉细胞表面的一个普遍特性，特定的连接形态是肌肉细胞与其粘附组织之间动态相互作用的结果。
