We shall begin our study of histology by examining the features of skeletal muscle. Skeletal muscle is an easily recog-
nizable tissue and some of what will be described for skeletal muscle can also be applied to the other muscle tissues.
Many of the proteins involved in muscle contraction are similar to proteins that function in the movements of cells in
general.
Three skeletal muscle cells or muscle fibers (myofibers) are shown in a longitudinal section in this micrograph. The
Downloaded
words cell and fiber are synonymous in reference to muscle and can be used interchangeably. Skeletal muscle cells
are multinucleated, and the nuclei are positioned at the periphery of the cytoplasm (arrow). Skeletal muscle cells are
also striated and the characteristic pattern of light and dark cross-striations can be clearly seen.
by
[Rutgers
University
Figure 2­2
130.219.8.11]
at
[04/08/15].
Copyright
©
McGraw-Hill
Global
Education
Holdings,
LLC.
Not
to
be
redistributed
or
modified
in
any
Connective tissue, a specialized type of tissue that fills in the spaces between the cells of the other types of tissue,
way
surrounds each muscle fiber. In skeletal muscle, this connective tissue is called the endomysium, or endomysial
without
connective tissue, and contains capillaries, fibroblasts and other elements of connective tissue proper, and the
terminal branches of nerve fibers. The endomysium constitutes a structure analogous to the basement membrane
(or basal lamina) of epithelial cells. For muscle tissue, the term external lamina is more appropriate than basal
permission.
lamina because there is no strict apical or basal region in regard to myocytes.
Within the cytoplasm (sarcoplasm) of the muscle cells, the myofibrils are visible as small, darkly stained structures
(arrows). Myofibrils are rod-shaped units that contain the proteins that interact to produce shortening of the cell.
Note the position of the nuclei of the skeletal muscle cells, here cut in cross-section. The peripheral location of the
nuclei is typical of normal skeletal muscle. The connective tissue between the bundles of muscle contains elongated
cells with densely stained nuclei (arrowhead). These cells are fibroblasts and will be discussed in the chapter on
connective tissue. Small blood vessels occupy the areas of connective tissue near the muscle cells.
19

---