How do tendons connect skeletal muscles to bones?

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Diagram showing the structure of human striated or skeletal muscle, with labeled cross-sections from whole muscle to fascicle, muscle fiber, myofibril, and sarcomere, highlighting actin and myosin filaments. — muscle The structure of striated, or skeletal, muscle. Striated muscle tissue, such as the tissue of the human biceps muscle, consists of long fine fibers, each of which is in effect a bundle of finer myofibrils. Within each myofibril are filaments of the proteins myosin and actin; these filaments slide past one another as the muscle contracts and expands. On each myofibril, regularly occurring dark bands, called Z lines, can be seen where actin and myosin filaments overlap. The region between two Z lines is called a sarcomere; sarcomeres can be considered the primary structural and functional unit of muscle tissue.

Tendons serve as the essential connective tissue that links skeletal muscle to bone, functioning to transmit the mechanical force generated by muscle contraction.1

The connection is achieved through a robust, hierarchical structure composed primarily of collagenous fibers. At the muscle end, the tendon is firmly integrated with muscle fibers. At the bone end, the tendon attaches via specialized collagenous fibers known as Sharpey fibers, which extend directly into the bone's matrix.1

This arrangement allows the tendon to withstand the significant stresses produced during movement. The tendon's internal organization—consisting of primary, secondary, and tertiary fiber bundles—is supported by a sheath called the endotenon, which enables the bundles to glide against one another, while the outer epitenon and paratenon layers facilitate movement against surrounding tissues.1