Page 312 - Atlas of Histology with Functional Correlations

(3), branching fibers (8), and a single central nucleus (6). The dark-staining

intercalated discs (2) connect individual cardiac muscle fibers (1). Small
myofibrils (4) are visible within each cardiac muscle fiber (1). The flattened and
fusiform cells surrounding the cardiac muscle fibers (1) represent the fibrocytes
of the endomysium (5). Although not visible in this illustration, delicate strands
of connective tissue endomysium surround the individual cardiac muscle fibers.

FIGURE 8.11 ■ Cardiac muscle (longitudinal section). Stain: Masson

trichrome. ×130.

FIGURE 8.12 | Cardiac Muscle in Longitudinal

Section

Comparison of the cardiac muscle fibers with skeletal muscles at higher
magnification and with the same stain (Fig. 8.4) illustrates the similarities and
differences between the two types of muscle tissue.

The cross-striations (1) are similar in both the skeletal and cardiac muscle

types but are less prominent in cardiac muscle fibers. The branching cardiac
fibers (9) are in contrast to the individual, elongated fibers of the skeletal
muscle. The characteristic intercalated discs (5, 7) of cardiac muscle fibers and

their irregular structure are more prominent at higher magnification. The
intercalated discs (5, 7) appear as either straight bands (5) or staggered (7) across
individual fibers.

The large, oval nuclei (3), usually one per cell, are centrally located in
cardiac fibers, in contrast to the multiple flattened and peripheral nuclei in

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