File:Cardiac muscle EM02.jpg

Cardiac Muscle Electron Micrograph

Electron micrograph of parts of three cat cardiac muscle fibers and an adjacent capillary in longitudinal section. This original historic (1969) EM^[1] has been relabeled to show key features in cardiac muscle ultrastructure. At the light microscope histology level, only the intercalated disc and some cross-striations can typically be seen using histological stains.

The cardiomyocytes (cardiac muscle cells) are packed with sarcomeres (for contraction) and mitochondria (for energy) with a nearby capillary for nutrient supply and waste removal.

• Image Top - In a cardiomyocyte (cardiac muscle cell) 2 contractile units (sarcomere) are shown by white arrows. The A and I bands, shown by black arrows, are the regions visible by light microscope as cross-striations.
• Image Bottom - The 2 cardiomyocytes (cardiac muscle cells) are coloured (labeled cell 1 and cell 2) and are joined by an intercalated disc.
• Image Bottom Right - A capillary (red) enclosed by an endothelial cell and its basement membrane contains a red blood cell.

Legend

• In D - Intercalated disc, the two lower cells are joined end to end by a typical steplike intercalated disc.
• Mt - Rows of mitochondria appear to divide the contractile substance into myofibril-like units but, unlike the true myofibrils of skeletal muscle, these branch and rejoin and are quite variable in width.
• Lp - Lipid droplets somewhat distorted in specimen preparation are found between the ends of the mitochondria.
• Cap - Capillary.

Original image X 15,000.

Links: EM Image | EM Image cells labeled | HM Practical - Cardiac Histology

Reference

1. ↑ D W Fawcett, N S McNutt The ultrastructure of the cat myocardium. I. Ventricular papillary muscle. J. Cell Biol.: 1969, 42(1);1-45 PMID:4891913 | PMC2107571

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Original article figure (FIG. 1) has been scaled and rotated. Labels and colours have also been added to the original image.