Where gap junctions are abundant, membranes stain darker and histologists named these areas intercalated disks . Cardiac myofibers also contain a single, centrally located nucleus in contrast to the multiple peripheral nuclei of skeletal muscles. In summary then, cardiac muscle consists of branching myofibers with single, centrally placed nuclei. Intercalated disks are visible between myofibers in longitudinal views and there are abundant capillaries in intercellular spaces. Cardiac muscle in longitudinal section showing striations and intercalated disks.
Capillaries are visible to the top and left margins of the image.
Enlarged view of cardiac muscle with striations and intercalated disks. Enlarged view showing a central nucleus and the clear perinuclear space . Cardiac muscle in cross-section . At this high magnification central nuclei and a clear perinuclear space can be seen. Two or three small capillaries adherent to the myofibers are also visible.