Synovial cells are classically defined as type A or type B synoviocytes.
Type A synoviocytes are macrophage-like and derived from the hematopoietic system. These cells contain multiple lysosomes and play a phagocytic role in removing particulate debris from the joint. Type B synoviocytes are fibroblastic in nature and derived from the mesenchyme. These cells also secrete the hyaluronic acid present in synovial fluid and in the matrix surrounding synovial cells.