Musculo

Musculo is a term used in anatomy and medicine to refer to muscle tissue, the soft contractile tissue responsible for movement and force generation. The word derives from the Latin musculus, meaning "little mouse," a reference to the way muscles appear to move beneath the skin. In several languages, including Italian (muscolo) and Spanish (músculo), cognate forms are used to denote muscle.

Muscles are classified into three main types: skeletal, smooth, and cardiac. Skeletal muscles attach to bones or skin, are usually under voluntary control, and are striated. Smooth muscles line the walls of hollow organs and vessels and operate involuntarily without striations. Cardiac muscle forms the walls of the heart; it is striated and contracts rhythmically without conscious input.

Muscle structure includes muscle fibers organized into fascicles, surrounded by connective tissue layers: endomysium, perimysium, and epimysium. Each fiber contains myofibrils composed of repeating sarcomeres, the basic contractile units made of actin and myosin. Contraction occurs through the sliding filament mechanism: calcium ions released from the sarcoplasmic reticulum enable myosin heads to pull on actin filaments, using ATP to shorten the sarcomere.

Nervous control is provided by motor neurons at the neuromuscular junction, where acetylcholine initiates an action potential that triggers contraction. Functions of muscle include movement, stabilization of joints, maintenance of posture, and heat production through metabolism. Muscles adapt to activity through hypertrophy and, in the absence of use, through atrophy; aging also leads to sarcopenia.

Muscle disorders include muscular dystrophies and various myopathies. Understanding muscle biology supports clinical medicine, physical therapy, sports science, and rehabilitation.