Anatomy and Chemistry Basics
Muscle Tissue
Due to its irregular arrangement of actin and myosin filaments, smooth muscle does not have the striated appearance of skeletal muscle. In addition, the sarcolemma does not form a system of transverse tubules. As a result, contraction is controlled and relatively slow; properties appropriate for smooth muscle function.
In addition to the thick myosin and thin actin filaments, smooth muscles also possess noncontracting intermediate filaments. The intermediate fibers attach to dense bodies that are scattered through the sarcoplasm and attached to the sarcolemma. During contraction, the movement of myosin and actin is transferred to intermediate fibers, which pull on the dense bodies, which, in turn, pull the muscle cell together. In this way, the dense bodies function similarly to the Z discs in striated muscles.
