CARDIAC MUSCLE – 1
Unlike skeletal muscle fibers, /strong>cardiac muscle fibers are relatively short cylinders whith somewhat flattened ends.
In longitudinal sections, their cytoplasm shows transverse striations similar to those of skeletal muscle fibers. However the striations are generally less conspicuous and may be more difficult to observe after Hematoxylin and eosin staining. Certain other types of stains reveal them very well.
Each cardiac muscle fiber usually contains one centrally located nucleus. This differs from skeletal muscle fibers, whose multiple nuclei are located at the cell periphery. The central position of the nuclei is particularly evident in both longitudinal and cross-sections.
Another characteristic feature of cardiac muscle fibers is the presence of intercalated discs. These appear as thick, darkly stained strong>transverse lines that are distinct from the regular striations. Intercalated discs are specialized junctional complexes located at the ends of cardiac muscle cells. They connect neighboring cells and help form the functional chains of cardiac muscle fibers. They contain several types of cell junctions, including adherens junctions and gap junctions.
In the heart, the fibers are organized into bundles organized in different directions.
In longitudinal sections, their cytoplasm shows transverse striations similar to those of skeletal muscle fibers. However the striations are generally less conspicuous and may be more difficult to observe after Hematoxylin and eosin staining. Certain other types of stains reveal them very well.
Each cardiac muscle fiber usually contains one centrally located nucleus. This differs from skeletal muscle fibers, whose multiple nuclei are located at the cell periphery. The central position of the nuclei is particularly evident in both longitudinal and cross-sections.
Another characteristic feature of cardiac muscle fibers is the presence of intercalated discs. These appear as thick, darkly stained strong>transverse lines that are distinct from the regular striations. Intercalated discs are specialized junctional complexes located at the ends of cardiac muscle cells. They connect neighboring cells and help form the functional chains of cardiac muscle fibers. They contain several types of cell junctions, including adherens junctions and gap junctions.
In the heart, the fibers are organized into bundles organized in different directions.
Lower figure:
Several bundles of longitudinally sectioned cardiac muscle fibers.
Notice cigar-shaped nuclei placed in the cell center.
As seen in longitudinal section
As seen in cross-section
Cardiac muscle in longitudinal section. Staining: HE. Small magnification.