Which membrane lines joint cavities?

• A. Mucous membrane
• B. Serous membrane
• C. Cutaneous membrane
• D. Synovial membrane

Answer: (D)

Line joint cavities is the function of the synovial membrane. In freely movable joints, the inner lining of the articular capsule is the synovial membrane, and it secretes synovial fluid into the joint space. This fluid lubricates the joint and nourishes the avascular articular cartilage, letting the surfaces glide smoothly and reducing wear during movement.

Other membranes have different roles: mucous membranes line cavities that open to the outside and often secrete mucus; serous membranes line closed body cavities and produce serous fluid for lubrication; the cutaneous membrane is the skin. The synovial membrane is specialized for producing lubricating fluid rather than forming a barrier or secreting mucus.