title: The membrane systems of the cardiac muscle cell of Tmetonyx cicada O. Fabricius (Crustacea, Amphipoda).
abstract: The membrane systems of the cardiac muscle cell of the amphipod Tmetonyx cicada (O. Fabricus) are described. The sarcolemma invaginates and forms a transverse network of tubules at the level of the Z band. Narrow longitudinal tubules branch from the network and connect to another transverse network of tubules at the H band level, where dyadic and triadic junctions are formed with the sarcoplasmic reticulum. Adjacent myofibrils are normally separated by a well developed double layer of the sarcoplasmic reticulum. In areas where the myofibrils closely approach the outer sarcolemma, peripheral couplings have been found at the level of the H band.
mesh_terms: D000818:Animals; D003445:Crustacea / Q000648:ultrastructure*; D008854:Microscopy, Electron; D009206:Myocardium / Q000648:ultrastructure*; D009210:Myofibrils / Q000648:ultrastructure; D012508:Sarcolemma / Q000648:ultrastructure; D012519:Sarcoplasmic Reticulum / Q000648:ultrastructure