Abnormal sarcomere morphology Abnormal Z disk morphology 2019-12-23T15:57:40Z Any structural anomaly of the Z disk, which is the platelike region of a muscle sarcomere to which the plus ends of actin filaments are attached. Z-discs (Z-disk, Z-line, Z-band) delineate the lateral borders of sarcomeres and are the smallest functional units in striated muscle. The core of a Z-disc consists of actin filaments coming from adjacent sarcomeres which are crosslinked by alpha-actinin molecules. Z-discs, which are difficult to detect in conventional light microscopy, appear in the longitudinal view of electron microscopy as electron dense bands with varying sizes, ranging from 30 to 50 nm in fast muscle and 100 t0 140 nm in slow muscle and cardiac myocytes.