8-3 Muscle tissue

SKELETAL MUSCLE – 1

The fibers of skeletal muscle are long, cylindrical cells that may reach several centimeters in length. They are multinucleated, and their nuclei are located at the periphery of the fiber, immediately beneath the plasma membrane. The nuclei contain relatively euchromatic (light-staining) chromatin and are elongated, with an elliptical or cigar-like shape.

The peripheral location of the nuclei is best appreciated in transverse-sections of skeletal muscle fibers, as shown in the second diagram and image.

A characteristic feature of skeletal muscle fibers is the presence of transverse striations (bands) in their cytoplasm. These striations are visible when the fibers are viewed in longitudinal sections.

The lower image shows a skeletal muscle section at low magnification. Most of the fibers are cross-sectioned, whereas a few fibers, highlighted in light blue, are longitudinally sectioned. Because the image was obtained at low magnification, the transverse striations of the longitudinally sectioned fibers cannot be clearly distinguished.

Fibers in longitudinal section

Fibers in cross section