Organization of skeletal muscle
Skeletal muscles are composed of many cells called muscle fibers, which are arranged in bundles called fascicles. These fascicles are surrounded by connective tissue called perimysium. Each muscle fiber is a single, elongated cell that is wrapped by a thin connective tissue layer called endomysium.
Muscle fibers are made up of many smaller structures called myofibrils, which are organized into repeating units called sarcomeres. Sarcomeres are the basic functional units of skeletal muscle, responsible for muscle contraction. Each sarcomere contains thick and thin filaments, which are arranged in a highly organized pattern of overlapping bands.
The thick filaments are made up of myosin, while the thin filaments are composed of actin, troponin, and tropomyosin. The sarcomere is anchored at either end by protein structures called Z-discs.
Skeletal muscle fibers are innervated by nerve cells called motor neurons, which stimulate muscle contraction. The point where the motor neuron meets the muscle fiber is called the neuromuscular junction.
The connective tissue that surrounds muscle fibers merges at the ends of the muscle to form tendons, which attach muscles to bones. When a muscle contracts, it pulls on the tendons, which in turn pull on the bone to create movement.
Overall, the organization of skeletal muscle is highly structured and organized, with many individual muscle fibers arranged in bundles, and many sarcomeres within each fiber responsible for muscle contraction. The innervation of muscle fibers by motor neurons, and the attachment of muscles to bones via tendons, are also critical features of the organization of skeletal muscle.