Final answer:
A synovial membrane is a thin connective tissue membrane that secretes synovial fluid for lubricating freely movable joints.
Step-by-step explanation:
The synovial membrane is a specialized connective tissue membrane that lines the inner surface of the joint cavity at a synovial joint and is crucial for the movement of freely movable joints, such as those found in the shoulder, elbow, and knee. This thin layer of cells is responsible for producing synovial fluid, a thick and slippery substance that provides lubrication, reduces friction, and nourishes the articular cartilage of the joint.
Unlike serous membranes that secrete serous fluid, the synovial membrane does not secrete mucus nor is it composed of multiple cell layers; hence it is neither mucus-secreting nor thick with layers.