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Medical Definition of Intercalated disc
1. An electron dense junctional complex, at the end to end contacts of cardiac muscle cells, that contains gap junctions and desmosomes. most of the disc is formed of a convoluted fascia adherens type of junction into which the actin filaments of the terminal sarcomeres insert (they are therefore equivalent to half Z bands), desmosomes are also present. The lateral portion of the stepped disc contains gap junctions that couple the cells electrically and thus coordinate the contraction. This entry appears with permission from the Dictionary of Cell and Molecular Biology (11 Mar 2008)