Cardiac muscle is restricted to the wall of the heart. it is also has cross-striations and is composed of elongated, branched individual cells that lie parallel to each other. Mature cardiac muscle cells are roughly 85 to 100 um long and 15 urn wide. Unlike multi-nucleated skeletal muscle, these cells posses only one or two centrally located nuclei, which lie deep at the center of the fiber. The sarcoplasm possesses abundant myofibrils and numerous mitochondria and glycogen granules. This is because they need a large amount of energy. Cardiac muscle fibers bear contractile filaments, which are same as those of skeletal muscle, they contain myosin and actin filament. A unique and distinguishing feature of cardiac muscle is the presence of specialized junctional complex at the ends of the adjacent muscle cells called intercalated discs. This discs hold the cells together between the adjacent fibers that allow rapid spread of excitation from one fiber to the next throughout the heart. Contraction of cardiac muscle in involuntary vigorous and rhythmic.
1 Answer June 10, 2019