[[FileFicheiro:Sarcomere.jpg|thumbminiatura|PortionEstrutura of adun [[myofibrilsarcómero]], showing [[sarcomere]] structure:<br/>'''S''' = SarcomereSarcómero, unitunidade offuncional muscledo functionmúsculo<br/>'''A''' = banda A-band, regionrexión ofda myosinmiosina<br/>'''I''' = banda I-band, regionrexión ofda actinactina<br/>'''H''' = zona H-zone, regionrexión ofde justsó myosinmiosina<br/>'''Z''' = liña Z-line, sarcomerelímite do boundarysarcómero<br/>'''M''' = liña M-line, sarcomerecentro centerdo sarcómero.]]
Os miocitos conteñen [[miofibrila]]s, que son longas cadeas de [[sarcómero]]s, as unidades contráctiles da célula. As miofibrilas das células do [[músculo liso]] non están dispostas en sarcómeros. Os sarcómeros están compostos de filamentos finos e grosos. Os finos están formados pola proteína [[actina]] e os grosos da proteína [[miosina]].
Each myocyte contains [[myofibrils]], which are very long chains of [[sarcomeres]], the contractile units of the cell. A cell from the [[biceps brachii muscle]] may contain 100,000 sarcomeres.<ref>Assuming that the length of biceps is 20 cm and the length of sarcomere is 2 micrometer, there are 100,000 sarcomeres along the length of biceps.</ref> The myofibrils of [[smooth muscle]] cells are not arranged into sarcomeres. The sarcomeres are composed of thin and thick filaments. Thin filaments are [[actin]] filaments, whereas thick filaments consist of an arrangement of [[myosin]] proteins. The sarcomere does not contain organelles or a nucleus. Individual muscle fibrils are surrounded by [[endomysium]].
Within the muscle cell, the myofibrils are bound together by [[perimysium]] into bundles called [[Muscle fascicle|fascicles]]; the bundles are then grouped together to form [[muscle tissue]], which is enclosed in a sheath of [[epimysium]]. [[Muscle spindle]]s are distributed throughout the muscles and provide sensory feedback information to the [[central nervous system]].
