- Discussion:
    - synovial fluid is an ultrafiltrate of blood plasma plus hyaluronic acid and glycoproteins;
    - synovial fluid resembles material in interstices of loose connective tissue in respect to both components;
    - rate and method of passage of substances into & out of synovial fluid depend upon the molecular size of the substance;
          - gases & crystalloids diffuse rapidly in both directions;
          - larger proteins appear to leave fluid by way of lymphatics;
          - particulate matter is taken up by macrophages, and its egress from the joint cavity is quite slow;
          - inflamed synovium contains large clefts which probably permit passage of molecules of almost any size;
    - one of main functions of the lining cells of synovium is to secrete certain components of the synovial fluid;
    - in addition to substances secreted by the lining cells, synovial fluid contains proteins that are electrophoretically and immunologically identical to plasma proteins;
         - these proteins come from blood that circulates in synovial membranes