The microfilament system is a network of filaments 6 nanometers (nm) in diameter that are important for anchoring plasma membrane proteins, for producing cell movement, and for cell division. The base filament is composed of a protein called actin that is 42 kilodaltons (kd) in weight.
It is divided into two subgroups; the single-unit (unitary) and multiunit smooth muscle. Within single-unit cells, the whole bundle or sheet contracts as a syncytium (i.e. a multinucleate mass of cytoplasm that is not separated into cells).mooth muscle is fundamentally different from skeletal muscle and cardiac muscle in terms of structure, function, regulation of contraction, and excitation-contraction coupling. Smooth muscle cells known as myocytes, have a fusiform shape and, like striated muscle, can tense and relax.
These muscles are striated and has many nuclei. Smooth muscles are not striated and are the muscles that are not in voluntary control. These include organs and blood vessels, excluding heart. These muscles are unstriated with one nucleus.Smooth muscles has only one nucleus.n the heart, the cardiac muscle pumps the blood into the arteries. The smooth muscles in blood vessels are used to pump blood in one direction (in veins, which is in low pressure, there are valves which prevents backflow).