Electron microscopic study of synovial lining cells in the developmental process.
In order to decide whether or not the two types of synovial lining cells originate from the same precursor cells, the developmental process of knee joint of rat fetus was studied electron microscopically and the following results were obtained. 1. Both type A and type B cells are derived from the same precursor cells that are synovioblasts. 2. The type B cells originate directly from synovioblasts. 3. There are intermediate type cells in the course of development of type A cells.