Light microscopy of the mandibular joint tissues from fetal mice show a distribution of fibrillar structures in the articular fibrous capsule covering the condylar head. Further SEM and TEM studies were conducted on autoclaved xiphoid and mandibular condylar processes of the fetuses for observation of the elastic system fibers in these cartilaginous tissues. SEM showed that non-collaginous fibers branched and united to form a complicated network in the cartilage. A fine structure study on diameter distribution of the fibers indicated elastogenesis in the differentiating cell layer and fiber maturation in the articular surfaces and calcification layer, thus suggesting a sequential development, growth, and degeneration of the cellular and fibrillar components in the cartilage, as well as bidirectional cell differentiation in the growing mandibular joint. A further TEM study on these autoclaved connective tissues showed the elastic system fibers in the network to be composed of fine microfibrils and amorphous elastin. The elastic fibers in the condylar cartilage were a loose network having many tortuous main and oblique elastic fibers, and coiling oxytalan fibers.
Animals Cartilage