It is formed of elongated cells in which the major physiological function is contraction. The muscle cells, or muscle fibers, are usually found in bundles or sheets bound together by varying amounts of connective tissue. The basic cellular unit of muscle tissue is the muscle fiber.
Every muscle fiber is surrounded by a basement membrane.
Within the sarcoplasm are cytoplasmic contractile elements, the myofilaments. On both a structural and a functional basis, muscle is classified as smooth, skeletal, or cardiac. You are expected to be able to distinguish these three muscle types both in cross section and longitudinal section. You are also expected to identify structures which are underlined in the following sections. The fibers of this type of muscle tissue are the largest of all muscle cells both in length and in diameter.