What Are the Different Types of Skeletal Muscle Tissue?

The human body has three different types of muscle tissue — cardiac, smooth, and skeletal. While these are distinct from one another, all human skeletal muscle tissue is referred to as striated muscle tissue. It is part of the musculoskeletal system and has several identifying characteristics to delineate it from other types of muscle tissue, such as its unique light and dark appearance.

Muscle tissues perform various functions throughout the body. Cardiac muscle is an involuntary muscle that is present in the heart and helps to synchronize the beating of the organ. Smooth muscle, also known as visceral muscle, is also involuntary and lines the arteries, digestive tract, and other organs. It is referred to as smooth because, unlike cardiac and skeletal muscle, it doesn’t have striations. The final type, skeletal muscle tissue, can be found in the various muscles of the human body, as its name indicates.

Striated or skeletal muscle tissue is responsible for the voluntary movement of various body parts. Voluntary movements, such as bending an arm or leg, are controlled by the individual and not the normal, automatic functioning of the body commonly associated with involuntary movements, such as the action of smooth muscles on digestion. This type can be found in the biceps, quadriceps, and pectoral muscles, among many others.

As a part of the musculoskeletal system, skeletal muscle tissue works in conjunction with bones and other supportive structures to help facilitate various movements of the human body. Muscles are attached to bones by tendons. When signaled, muscle fibers contract, resulting in the movement of the tendon and attached bone to accomplish the required movement.

The term 'striated muscle' comes from the fact that skeletal muscle tissue consists of fibers with both light and dark properties. Bundles of myofibrils are contained within each muscle fiber. Within each myofibril, thick filaments of myosin and thin filaments of actin contribute to the makeup of the sarcomere, the functional unit of muscle fibers. All of these characteristics contribute to the striated appearance of skeletal muscle tissue.

There is more to this tissue than muscle fibers consisting of actin and myosin, however. The contraction of skeletal muscles is directly related to the functioning of neuromuscular junctions. This is where the various motor neurons attach to muscles. As nerve impulses reach the neuromuscular junction, acetylcholine is released to attach to the receptors on the surface of the muscle cells. This produces an electrical impulse that results in a muscle contraction.