In skeletal muscle, each muscle cell, more commonly called a muscle fiber, is actually a multinucleated syncytium. A muscle fiber is formed during development by the fusion of small, individual muscle cells called myoblasts (see page 326). When viewed in cross section, the mature multinucleated muscle fiber reveals a polygonal shape with a diameter of 10 to 100 m (Plate 21, page 340). Their length varies from almost a meter, as in the sartorius muscle of the lower limb, to as little as a few millimeters, as in the strapedius muscle of the middle ear. (Note: A muscle fiber should not be confused with a connective tissue fiber; muscle fibers are skeletal muscle cells, whereas connective tissue fibers are extracellular products of connective tissue cells.)
The nuclei of a skeletal muscle fiber are located in the cy-branches are present within the endomysium, running paral toplasm immediately beneath the plasma membrane, also called the sarcolemma. In the past, the term sarcolemma was used to describe a thick “membrane” that was thought to be the cytoplasmic boundary of the muscle cell. It is now known that the thick sarcolemma actually represents the plasma membrane of the cell, its external lamina, and the surrounding reticular lamina.
A skeletal muscle consists of striated muscle fibers held together by connective tissue.
The connective tissue that surrounds both individual muscle fibers and bundles of muscle fibers is essential for force transduction (Fig. 11.2). At the end of the muscle, the connective tissue continues as a tendon or some other arrangement of collagen fibers that attaches the muscle, usually to bone. A rich supply of blood vessels and nerves travels in the connective tissue.
The connective tissue associated with muscle is named according to its relationship with the muscle fibers:  Endomysium is the delicate layer of reticular fibers that im mediately surrounds individual muscle fibers (see Fig. 11.2a).
Only small-diameter blood vessels and the finest neuronal lel to the muscle fibers.
 Perimysium is a thicker connective tissue layer that surrounds a group of fibers to form a bundle or fascicle. Fascicles are functional units of muscle fibers that tend to work together to perform a specific function. Larger blood vessels and nerves travel in the perimysium.
 Epimysium is the sheath of dense connective tissue that surrounds a collection of fascicles that constitutes the muscle (see Fig. 11.1a). The major vascular and nerve supply of the muscle penetrates the epimysium.
Three types of skeletal muscle fibers—red, white, and intermediate—can be identified by color in vivo.