Intercalated discs are seen as bars that run transversely through the cardiac muscle fibers. They are formed by long junctional complexes and delimit the ends of each cardiac muscle fiber.
These structures are best highlighted with various stains, such as iron hematoxylin and phosphotungstic hematoxylin (which was used to prepare the section seen on this page).
The image shows cardiac muscle fibers sectioned longitudinally.
The transverse striation (bands) of the cardiac fibers, similar to that of skeletal muscle fibers, becomes very evident when these staibns are used.
In addition, there are dark, thicker lines of varying sizes arranged transversely across the fibers. These are the intercalated discs and appear highlighted in white.
Intercalated discs are not always easy to recognize in cross-sections of fibers stained with HE.
Cardiac muscle. Staining: Phosphotungstic hematoxylin. Magnification: medium.
