Which substance acts as a cushion and prevents wear on the surfaces of joints?

The substance that acts as a cushion and prevents wear on the surfaces of joints is cartilage. Cartilage is a flexible connective tissue found in various parts of the body, including the joints. It provides a smooth, slippery surface that enables bones to glide over one another with minimal friction during movement. This cushioning effect helps absorb shock and reduces wear and tear on the joint surfaces, thereby playing a crucial role in maintaining joint health and function.

In contrast, tendons connect muscles to bones and are primarily involved in transmitting forces generated by muscle contractions, but they do not serve as cushioning materials. Bone marrow, located within the cavities of bones, is responsible for producing blood cells but does not play a direct role in joint cushioning. Synovial fluid, while it lubricates joints and provides some cushioning effects, is not the structural component that acts as a cushion; instead, it is found within the joint cavity and works alongside cartilage to reduce friction during movement. Thus, cartilage is the primary structure responsible for cushioning and protecting the joints.