Fast twitch muscle

Skeletal striated muscle
A top-down view of skeletal muscle
Details
Latin	muscularis striatus skeletalis
TH	H2.00.05.2.00002
Anatomical terminology []

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

A skeletal muscle refers to multiple bundles of cells called muscle fibers (fascicles). The fibres and muscles are surrounded by connective tissue layers called fasciae. Muscle fibres, or muscle cells, are formed from the fusion of developmental myoblasts in a process known as myogenesis. Muscle fibres are cylindrical, and have more than one nucleus.

Muscle fibers are in turn composed of myofibrils. The myofibrils are composed of actin and myosin filaments, repeated in units called sarcomeres, which are 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.

Connective tissue is present in all muscles as fascia. Enclosing each muscle is a layer of connective tissue known as the epimysium; enclosing each fascicle is a layer called the perimysium, and enclosing each muscle fiber is a layer of connective tissue called the endomysium.

Muscle fibres are the individual contractile units within muscle. A single muscle such as the biceps contains many muscle fibres.