As previously noted, the intercalated disc represents the attachment site between cardiac muscle cells. In the light microscope, the disc appears as a densely staining linear structure that is oriented transversely to the muscle fiber. Often it consists of short segments arranged in a steplike fashion (Fig. 11.16). When the site of the intercalated disc is examined with the TEM, the densely staining structure seen in the light microscope can be attributed to the presence of a transverse component that crosses the fibers at a right angle to the myofibrils. The transverse component is analogous to the risers of the stairway. A lateral component (not visible in the light microscope) occupies a series of surfaces perpendicular to the transverse component and lies parallel to the myofibrils. The lateral component is analogous to the steps of the stairway. Both components of the intercalated disc contain specialized cell-to-cell junctions between adjoining cardiac muscle cells:  Fascia adherens (adhering junction) is the major constituent of the transverse component of the intercalated disc and is responsible for its staining in routine H&E