synovia
A transparent, slightly yellow viscous fluid contained within a membrane enclosing a movable joint, a bursa or a tendon sheath. Synovial fluid contains hyaluronic acid secreted by the synovial membrane, and interstitial fluid derived from blood plasma. Synovial fluid has many functions; it lubricates and nourishes cartilage in the joint; it bears most of the weight at joint surfaces, preventing the articular cartilages from touching each other, thereby minimizing friction and damage; and the fluid contains cells that can devour microbes and the cell debris resulting from wear and tear during joint activity (see phagocytosis).
