CARDIAC MUSCLE
Figure 2­28
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Holdings,
Cardiac muscle, like skeletal muscle, is striated and contains transverse stripes corresponding to the light I bands
and dark A bands in skeletal muscle fibers and myofibrils. Unlike skeletal muscle, which is composed of multinuc-
LLC.
leated cells, cardiac muscle consists of individual cells separated from one another by cell-to-cell junctions called
intercalated discs, which are characteristic of cardiac muscle. Neither skeletal muscle nor smooth muscle has in-
Not
tercalated discs. In this relatively low magnification of a longitudinal section through the myocardium, the arrow
to
be
indicates an intercalated disc, which is a specialized region of the sarcolemma that forms the junction of one cell
redistributed
(myofiber or myocyte) with another.
The myofibers contain a single nucleus located in the center of the cell. This is different from skeletal muscle, which
is multinucleated with the nuclei positioned just under the sarcolemma at the periphery of the cell.
or
modified
Cardiac myofibers can branch, as opposed to skeletal fibers, which do not and are cylindrical in shape. Cardiac
muscle, like skeletal muscle, has a rich vascular supply. Sympathetic and parasympathetic nerve endings can be
in
located in cardiac muscle.
any
way
without
permission.
47

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