Tendons attach _______ to _______.

Tendons play a crucial role in the musculoskeletal system by attaching muscles to bones. This attachment is essential for movement because when a muscle contracts, it pulls on the tendon, which in turn pulls on the bone, resulting in motion of that bone at the joint. This connective tissue is composed primarily of collagen fibers, providing strength and resilience, allowing the force generated by the muscle to be effectively transmitted to the bone.

The other options do not accurately represent the function of tendons. For instance, tendons do not attach bone to bone or muscle to muscle; these functions are carried out by ligaments, which connect bones at joints. Additionally, while the skin plays a role in various anatomical systems, it does not directly connect to bone through tendons. Therefore, the correct answer highlights the fundamental anatomical relationship that tendons establish, which is essential for enabling locomotion and stabilization of the skeletal system.