Light micrograph of a human synovial membrane (innermost part of the joint capsule). It delimits the joint cavity of the diarthrosis. In the vicinity of the lumen of the joint cavity, a band of synovial cells is concentrated, adopting an appearance reminiscent of a lining epithelium, however, these synovial cells are conjunctive tissue cells that form a discontinuous lining. At left is a space occupied by loose connective tissue with dilated blood vessels with abundant red cells in the lumen, indicating congestion.