A mature contractile cell, which has as part of its cytoplasm myofibrils organized in various patterns. Found in muscle tissue, myocytes are long, tubular cells that arise developmentally from myoblasts to form muscle. There are specialized forms: cardiac, skeletal, and smooth muscle myocytes, with various properties. [ XAO:curators http://purl.obolibrary.org/obo/CL_0000187 ]