Arthropods have an open circulatory system with a simple tubular heart, so it has been estimated that the contractile pumping structure of the cardiac muscle will be less efficient than that of vertebrates. Nevertheless, certain arthropods are known to have far superior properties and characteristics than vertebrates, so we investigated the fine structural features of intercalated discs and cardiac junctions of cardiac muscle cells in the black widow spider Latrodectus mactans. Characteristically, the spider cardiac muscle has typical striated features and represents a functional syncytium that supports multiple connections to adjacent cells by intercalated discs. Histologically, the boundary lamina of each sarcolemma connects to the basement membrane to form an elastic sheath, and the extracellular matrix allows the cells to be anchored to other tissues. Since the intercalated disc is also part of sarcolemma, it contains gap junctions for depolarization and desmosomes that keep the fibers together during cardiac muscle contraction. Furthermore, fascia adherens and macula adherens (desmosomes) were also identified as cell junctions in both sarcolemma and intercalated discs. To enable the coordinated heartbeat of the cardiac muscle, the muscle fibers have neuronal innervations by multiple axons from the motor ganglion.

中文翻译：

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黑寡妇蜘蛛 Latrodectus mactans 闰盘和心脏连接处的精细结构


节肢动物具有开放式循环系统和简单的管状心脏，因此据估计，心肌的收缩泵送结构的效率将低于脊椎动物。尽管如此，某些节肢动物已知具有比脊椎动物优越得多的特性和特征，因此我们研究了黑寡妇蜘蛛 Latrodectus mactans 心肌细胞的闰盘和心脏连接的精细结构特征。从特征上看，蜘蛛心肌具有典型的横纹特征，代表功能性合胞体，通过闰盘支持与相邻细胞的多个连接。在组织学上，每个肌膜的边界层连接到基底膜，形成弹性鞘，细胞外基质允许细胞锚定到其他组织。由于闰盘也是肌膜的一部分，因此它包含用于去极化的间隙连接和在心肌收缩期间将纤维保持在一起的桥粒。此外，筋膜粘附和黄斑粘附（桥粒）也被鉴定为肌膜和闰盘中的细胞连接。为了使心肌协调心跳，肌纤维具有来自运动神经节的多个轴突的神经元神经支配。