Cardiac muscle is striated, involuntary muscle found in the heart wall. Cardiac muscle cells (or cardiomyocytes) contain the same contractile filaments as in skeletal muscle. Cardiac muscle cells are intermediate in size compare to skeletal and smooth muscle.
Intercalated Discs - cardiac muscle cells are joined together by specialized junctions called intercalated discs. They appear as thin, dark stained linear structures dividing adjacent cells that are perpendicular to the direction of the muscle fiber
Lipofuscin Pigment - residue of lysosomal digestion that accumulates as yellow-brown granules near the nucleus of some cells. In this specimen, few cells have detectable amounts.