myocyten

Myocyten, or myocytes, are the basic contractile cells of muscle tissue. They occur in three broad categories: skeletal, cardiac (cardiomyocytes), and smooth. All myocytes share a contractile apparatus built from actin and myosin arranged into sarcomeres, but they differ in structure, control, and location.

Skeletal myocytes are long, cylindrical cells that are multinucleated and formed by fusion of myoblasts during development. They are striated and capable of rapid, forceful contractions under voluntary control. They are organized into bundles (fascicles) and rely on extensive neuromuscular innervation and a rich capillary network for function and endurance.

Cardiac myocytes are the muscle cells of the heart. They are typically smaller, often mono- or bi-nucleated, and are branched and interconnected by intercalated discs that contain gap junctions and desmosomes. This arrangement enables synchronized, rhythmic contractions essential for pumping blood. They are striated and rely on calcium-induced calcium release for contraction; most rely on aerobic metabolism and have limited regenerative capacity.

Smooth muscle myocytes are spindle-shaped, uninucleate cells that lack striations. They form layers in the walls of hollow organs and vessels. Contractions are typically slower and sustained, controlled by the autonomic nervous system and various hormones. Smooth muscle cells can proliferate in response to injury or growth cues.

Development and turnover: myocytes arise from mesodermal progenitors. Skeletal muscle fibers form by myoblast fusion; cardiac myocytes largely end up as a non-proliferative population after birth; smooth muscle can remodel and proliferate. Pathology affecting myocytes, such as myocardial infarction damaging cardiac myocytes or muscular dystrophy affecting skeletal myocytes, underpins many cardiovascular and neuromuscular diseases.