Disorders of the Skeletal Muscle

Musculoskeletal disorders involve injuries to skeletal muscles and connective tissues from biomechanical stresses, accidents, or overuse, affecting localized areas. Neuromuscular disorders affect neurons controlling voluntary muscles or muscle-neuron interactions, typically have genetic causes, and impact most or all muscles in the body.

Muscle strains result from sudden events like accidental slipping or intense exercise, causing direct damage to muscle fibers. Tendonitis develops from repetitive movements, such as overuse of the knee and wrist in athletes, causing inflammation of the local tendons rather than muscle fiber damage.

Duchenne muscular dystrophy results from genetic mutations affecting the dystrophin protein, which maintains muscle cell structural integrity. Dystrophin deficiency compromises muscle fiber stability and strength, leading to progressive muscle degeneration, weakness, and gradual loss of muscle mass throughout the body.

Myasthenia gravis is an autoimmune disease where the immune system produces antibodies that block acetylcholine receptors at the neuromuscular junction. This prevents nerve signals from reaching muscles, resulting in muscle weakness, drooping eyelids, difficulty swallowing, and impaired voluntary muscle control.

Musculoskeletal injuries arise from biomechanical stresses including accidental events like slipping, intense physical activity, and overuse. Mundane activities such as excessive walking, prolonged sitting, and lifting objects can also injure muscles or tendons, particularly when combined with repetitive movements or improper technique.

Neuromuscular disorders have genetic causes and disrupt the neurons controlling voluntary muscles or the interactions between muscles and neurons. Since these neurons innervate most or all skeletal muscles throughout the body, genetic defects affect muscle function broadly rather than in isolated regions.

Dystrophin maintains the structural integrity and stability of muscle cells. When dystrophin is deficient or absent due to genetic mutation, muscle fibers lose structural support, become unstable, and undergo progressive degeneration, leading to the weakness and muscle loss characteristic of Duchenne muscular dystrophy.