Skeletal muscle

Skeletal muscle is a form of striated muscle tissue which is under the voluntary control of the somatic nervous system. It is one of three major muscle types, the others being cardiac muscle and smooth muscle. Most skeletal muscles are attached to bones by bundles of collagen fibers known as tendons.

Skeletal muscle is made up of individual muscle cells or myocytes, known as muscle fibers. They are formed from the fusion of developmental myoblasts (a type of embryonic progenitor cell that gives rise to a muscle cell) in a process known as myogenesis. Muscle fibres are cylindrical, and multinucleated.

Muscle fibers are in turn composed of myofibrils. The myofibrils are composed of actin and myosin filaments, repeated in units called sarcomeres, the basic functional units of the muscle fiber. The sarcomere is responsible for the striated appearance of skeletal muscle, and forms the basic machinery necessary for muscle contraction. The term muscle refers to multiple bundles of muscle fibers called fascicles. All muscles also contain connective tissue arranged in layers of fasciae. Each muscle is enclosed in a layer of fascia; each fascicle is enclosed by a layer of fascia and each individual muscle fiber is also enclosed in a layer of fascia.