Final answer:
The envelope enclosing the synovial joint cavity is known as the joint capsule, which is essential for movement and stability in synovial joints like the knee. It contains synovial fluid that lubricates the joint, and its fibrous tissue provides support.
Step-by-step explanation:
An envelope, attached to the end of each bone at the joint, enclosing the cavity of a synovial joint, is known as the joint capsule. This structure is essential in synovial joints, where it provides several key functions. Firstly, the joint capsule is a fibrous connective tissue that encapsulates the joint cavity, which contains synovial fluid. This fluid serves as a lubricant to reduce friction and allow for smooth joint movement. Secondly, the capsule maintains joint stability by attaching to each bone just outside the area of the articulating surface and can contain intrinsic ligaments that further enhance its stability.
Synovial joints, such as the knee, elbow, and shoulder, exhibit the greatest range of motion of all types of joints. They consist of a synovial membrane, an articular capsule, a joint cavity with synovial fluid, articular cartilage covering the bone ends, and ligaments supporting the joint structure. These components work together to facilitate movement while protecting the joint from dislocation and degradation.
Options for the envelope's identity include the bursa—a fluid-filled sac that reduces friction between tissues of the body, the synovial membrane—which lines the inner surface of the joint capsule and secretes synovial fluid, and the meniscus—a curved fibrocartilage structure within certain synovial joints that aids in distributing the pressure. However, based on multiple references to the joint cavity being enclosed by a connective tissue structure attached to the bone ends, the correct answer is 'C. Joint capsule'.