muskel

Muskel is the German term for muscle, a soft tissue that can contract to produce force and movement. In humans, muscles enable locomotion, posture, and various internal functions. Muscles are organized into three broad types: skeletal muscles, which attach to bones and are under voluntary control; smooth muscles, which regulate movements inside organs and vessels and are usually not under conscious control; and cardiac muscle, which makes up the heart and contracts rhythmically and involuntarily.

Muscle tissue is composed of muscle fibers (muscle cells) arranged in long bundles. Skeletal muscle fibers contain myofibrils organized into sarcomeres, the basic contractile units. Contraction occurs via the sliding filament mechanism, where myosin heads pull actin filaments, shortening the sarcomere. This process requires energy in the form of ATP and is regulated by calcium ions released in response to neural or hormonal signals. Skeletal muscles connect to bones through tendons, and their contraction produces movement by acting across joints.

Control and metabolism: Skeletal muscles are innervated by motor neurons at neuromuscular junctions. Blood vessels supply oxygen and nutrients, supporting aerobic and anaerobic energy production. Muscle fibers can adapt to use different energy pathways and can grow larger (hypertrophy) with training, or shrink with disuse (atrophy).

Development and health: Muscle tissue originates from mesodermal cells in the embryo and differentiates into myoblasts that fuse to form multinucleated fibers. Common conditions affecting muscle include muscular dystrophy, myopathies, cramps, and tendinopathies, among others.