Final answer:
Tendons are the structures in living animals that collect the activity of muscle fibers and connect muscles to bones, enabling skeleton movement when muscles contract.
Step-by-step explanation:
In the living animal, it is tendons that harness and collect the activity of muscle fibers. Tendons are strong bands of connective tissue that connect muscles to bones, transferring the tension from muscle contractions to the periosteum of bones to enable movement. This unique structure allows the force generated by contracting muscle fibers to be effectively transferred, causing the skeleton to move. The tendons work in concert with the collagen in the layers of tissue called the mysia, with one end integrated with muscle fibers and the other with bones.
While tendons are responsible for connecting muscles to bones, ligaments join bones to each other, and cartilage is a different form of connective tissue that provides support and flexibility in certain parts of the body, such as joints. Fascia, another kind of connective tissue, envelops muscles and separates them from other internal structures. When skeletal muscles contract, the fascicles and individual muscle fibers within them shorten, pulling on the tendons and, subsequently, the bones they are attached to, facilitating movement.