High resolution scanning electron microscopy of elastic cartilage

The elastic cartilage of the rat epiglottis was studied with a high-resolution SEM technique. The chondrocytes were found to be anchored in their lacunae by fibrils running in from the territorial matrix. This matrix exhibited a dense network of fibrils arranged tangentially around the lacunar cavity. The fibrils of the inter-territorial matrix however, formed a three dimensional network of sheets with interconnecting fibrils. The SEM has shown up for the first time a substructure in the fibrils in the form of circular protuberances arranged circumferentially around the fibrils and forming ridges 12--19 nm apart. We suggest that the fibrils are collagen, and the protuberances are the proteoglycans attached to the collagen fibrils. Globules seen attached to the fibrils are most probably 'matrix granules' as observed in other kinds of cartilage. The total inability to visualize elastin with the high resolution SEM is puzzling.