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A muscle cell, also known as a myocyte, is a mature contractile cell in the muscle of an animal. [1] In humans and other vertebrates there are three types: skeletal, smooth, and cardiac (cardiomyocytes). [2] A skeletal muscle cell is long and threadlike with many nuclei and is called a muscle fiber. [3]
Skeletal muscle cells are the individual contractile cells within a muscle, and are often termed as muscle fibers. [3] A single muscle such as the biceps in a young adult male contains around 253,000 muscle fibers. [22] Skeletal muscle fibers are multinucleated with the nuclei often referred to as myonuclei.
A myofibril (also known as a muscle fibril or sarcostyle) [1] is a basic rod-like organelle of a muscle cell. [2] Skeletal muscles are composed of long, tubular cells known as muscle fibers, and these cells contain many chains of myofibrils. [3] Each myofibril has a diameter of 1–2 micrometres. [3]
The fibres of striated muscle have a cylindrical shape with blunt ends, whereas those in smooth muscle are spindle-like with tapered ends. Striated muscle tissue has more mitochondria than smooth muscle. Both smooth muscle cells and cardiac muscle cells have a single nucleus, and skeletal muscle cells have many nuclei. [6]
Skeletal muscle, is a type of striated muscle, composed of muscle cells, called muscle fibers, which are in turn composed of myofibrils. Myofibrils are composed of sarcomeres, the basic building blocks of striated muscle tissue. Upon stimulation by an action potential, skeletal muscles perform a coordinated contraction by shortening each sarcomere.
Muscle contraction ends when calcium ions are pumped back into the sarcoplasmic reticulum, allowing the contractile apparatus and, thus, muscle cell to relax. Upon muscle contraction, the A-bands do not change their length (1.85 micrometer in mammalian skeletal muscle), [5] whereas the I-bands and the H-zone shorten. This causes the Z-lines to ...
The sarcoplasmic reticulum is a network of the tubules that extend throughout muscle cells, wrapping around (but not in direct contact with) the myofibrils (contractile units of the cell). Cardiac and skeletal muscle cells contain structures called transverse tubules (T-tubules), which are extensions of the cell membrane that travel into the ...
Striated skeletal muscle cells in microscopic view. Skeletal muscle is broadly classified into two fiber types: type I (slow-twitch) and type II (fast-twitch). Type I, slow-twitch, slow oxidative, or red muscle is dense with capillaries and is rich in mitochondria and myoglobin, giving the muscle tissue its characteristic red color.