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The sarcomere represents the basal contractile unit of striated muscles. A single myofibril is composed of these short structural units arranged end to end, which contract due to the relative sliding of thick (myosin) over thin (actin) filaments. The mammalian sarcomere is ~ 2 mm in length, and can shorten to ~ 70% of its original length during contraction. Structural features of the sarcomere include bundles of parallel thick and thin filaments assembled by two transverse structures, the Z lines and M lines. The Z lines and the M lines are connected by transverse filaments to the sarcolemma or to the neighboring myofibrils. Sarcomeres give to skeletal and cardiac muscles their striated appearance with I bands surrounding the Z lines, followed by A bands. The A bands contain a paler region called the H zone and in the middle the M line.


› Cellular component

Gene Ontology


sarcomere [ GO:0030017 ]
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