Muscle Cells

A muscle is composed of bundles of specialized cells capable of contraction and relaxation to create movement. There are three types of muscle in the body: skeletal, smooth, and cardiac. There are only three basic types of muscle: the striped, or striated, skeletal muscles that move the bones; the smooth, involuntary muscles that line the blood vessels, stomach, digestive tract, and other internal organs; and the cardiac muscles, which are a cross between the smooth and the striped muscles. If one were to slice through a muscle diagonally, he would find that it resembles a telephone cable. Inside is a bundle of smaller cables, and each bundle surrounds still smaller ones. The first and largest bundle is made up of muscle fibers in which there are nerves, blood vessels, and connective tissue. Each fiber is built up from smaller strands called myofibrils, and each myofibril contains interlaced filaments of muscle proteins. Visceral tissue is tissue associated with the internal organs of the body, especially those in the abdominal cavity.