Lihassolut

Lihassolut (Finnish for muscle cells) are specialized cells responsible for generating force and producing movement in animals. They convert chemical energy into mechanical work through coordinated contraction, and contribute to posture, locomotion, circulation and thermoregulation.

There are three principal types: skeletal muscle cells, which are long, multinucleated and striated and under voluntary control; cardiac muscle cells, which are branched, striated and linked by intercalated discs to permit coordinated, rhythmic contraction; and smooth muscle cells, which are spindle-shaped, non-striated and mediate involuntary contractions in blood vessels, the gastrointestinal tract and other organs.

At the cellular level lihassolut contain a plasma membrane (sarcolemma), cytoplasm (sarcoplasm) rich in mitochondria, and a specialized endoplasmic reticulum (sarcoplasmic reticulum) that stores calcium. Contractile apparatus is organized into myofibrils made of repeating sarcomeres composed mainly of actin and myosin filaments. Contraction follows the sliding filament mechanism, regulated by intracellular calcium and ATP-dependent cross-bridge cycling.

Lihassolut develop from myoblast precursors during embryogenesis, and some tissues retain satellite cells or other progenitors for repair. Their metabolic profile varies from oxidative to glycolytic depending on fiber type and activity. Dysfunction of lihassolut underlies many clinical conditions, including hereditary myopathies, inflammatory myositis, disuse atrophy and age-related sarcopenia, and they are a major focus of research in exercise physiology and regenerative medicine.