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 image shows the transverse striation (bands) of the cardiac fibers, similar to that of skeletal muscle fibers.
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 difficult to see in cross-sections of the fibers.
Cardiac muscle. Staining: Phosphotungstic hematoxylin. Magnification: medium.
