Part 3/14:
Skeletal muscles are highly organized, with their tissue structure composed of bundles of fibers. Each fiber contains cylindrical units called myofibrils, which further organize into repeating segments known as sarcomeres—the fundamental contractile units. The sarcomere's arrangement of actin (thin filaments) and myosin (thick filaments) gives skeletal muscles their characteristic striated pattern.
Microscopic examination reveals a layered organization: muscle fibers are bundled within fascicles surrounded by connective tissues like the epimysium, and within fibers, the myofibrils are made of sarcomeres. Each muscle fiber contains multiple nuclei, a feature that contributes to its capacity for repair and growth.