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A sarcomere (Greek σάρξ sarx "flesh", μέρος meros "part") is the smallest functional unit of striated muscle tissue. [1] It is the repeating unit between two Z-lines. Skeletal muscles are composed of tubular muscle cells (called muscle fibers or myofibers) which are formed during embryonic myogenesis.
Striated muscle tissue is a muscle tissue that features repeating functional units called sarcomeres. The presence of sarcomeres manifests as a series of bands visible along the muscle fibers, which is responsible for the striated appearance observed in microscopic images of this tissue.
A smooth-muscle cell is a spindle-shaped myocyte with a wide middle and tapering ends, and a single nucleus. Like striated muscle, smooth muscle can tense and relax. In the relaxed state, each cell is 30–200 micrometers in length, some thousands of times shorter than a skeletal muscle cell. [1]
This is thousands of times shorter than skeletal muscle fibers. The diameter of their cells is also much smaller which removes the need for T-tubules found in striated muscle cells. Although smooth muscle cells lack sarcomeres and myofibrils they do contain large amounts of the contractile proteins actin and myosin.
T-tubules (transverse tubules) are extensions of the cell membrane that penetrate into the center of skeletal and cardiac muscle cells.With membranes that contain large concentrations of ion channels, transporters, and pumps, T-tubules permit rapid transmission of the action potential into the cell, and also play an important role in regulating cellular calcium concentration.
[2] [3] The skeletal muscle cells are much longer than in the other types of muscle tissue, and are also known as muscle fibers. [4] The tissue of a skeletal muscle is striated – having a striped appearance due to the arrangement of the sarcomeres. A skeletal muscle contains multiple fascicles – bundles of muscle fibers.
Skeletal muscle, or "voluntary muscle", is a striated muscle tissue that primarily joins to bone with tendons. Skeletal muscle enables movement of bones, and maintains posture . [ 1 ] The widest part of a muscle that pulls on the tendons is known as the belly .
Cardiac muscle (also called heart muscle or myocardium) is one of three types of vertebrate muscle tissues, the others being skeletal muscle and smooth muscle. It is an involuntary, striated muscle that constitutes the main tissue of the wall of the heart. The cardiac muscle (myocardium) forms a thick middle layer between the outer layer of the ...