[The anatomical substrate of muscle contractility].

Muscle fiber action participates in a true contractile machinery associated with noncontractile components providing mechanical stability. The myofibril, the muscle fiber subentity, has an extremely consistent architecture, composed of longitudinal cylindrical units called sarcomeres, the skeletal muscle length functional unit, a highly important place in the transduction of chemical signal into mechanical contractile energy, for the most part mediated by calcium. The sarcoplasmic reticulum is the other major component of muscle fiber and is dedicated to calcium storage, liberation and distribution to the fiber, under the influence of action potential propagation. This phenomenon is called excitation-contraction coupling. This paper explores muscle anatomy from its main embryologic stages of development to its histochemical specificity, including its molecular constitution, and details the main morphofunctional relations supporting muscle contraction.