Muscles

The chapter comprehensively overviews various muscle tissues, their properties, innervation, nomenclature, and clinical relevance. It begins with an in-depth examination of skeletal muscle tissue, characterized by its striated appearance and voluntary control. These muscles are attached to bones and facilitate body movement and posture. Skeletal muscle fibers are multinucleated and can extend up to 30-35 cm long, with contraction initiated by motor nerve impulses from the brain or spinal cord. In contrast, smooth muscle tissue is non-striated and involuntary. It is found in the walls of internal organs and blood vessels, contributing to functions such as peristalsis and vasoconstriction. Smooth muscle cells are spindle-shaped, containing a single, centrally located nucleus. Contractions in these muscles are slower and more sustained than skeletal muscles, influenced by autonomic nerve impulses, hormones, and local metabolites. Cardiac muscle tissue, unique to the heart, combines skeletal and smooth muscle tissue features. It is striated like skeletal muscle but operates involuntarily like a smooth muscle. Cardiac muscle fibers are branched and connected by intercalated discs, allowing synchronized contractions necessary for adequate blood pumping. The properties of muscle tissue are discussed, highlighting their composition (approximately 75% water), primary energy sources (ATP, phosphocreatine, and glycogen), and various physiological functions. Muscle tissue is critical in movement, posture, joint stabilization, and thermoregulation. It also has unique cellular structures such as the sarcolemma, sarcoplasm, and sarcosomes. The innervation of muscles is crucial for their function, involving motor neurons that transmit impulses to muscle fibers, initiating contraction. The chapter delves into the detailed terminology of muscles, categorized based on factors such as shape, fiber orientation, location, function, size, length, and points of origin and insertion. Finally, the clinical information section emphasizes the importance of muscle anatomy in diagnosing and treating musculoskeletal disorders. It highlights the relevance of understanding muscle terminology and structure for effective medical interventions and rehabilitation.