Fine structural analysis of the conjunctival papillae in the chick embryo: A reassessment of their morphogenesis and developmental significance

Development and regression of the conjunctival papillae have been examined with both light and electron microscopy. The fibrous strands which extend from the papillae to the mesenchyme of the pre‐ossicular plate have been identified as collagen. Furthermore, the initial deposition of collagen fibrils has been shown to occur within channels between cells of the basal epithelium during stages 2 and 3. Bundles of collagen fibrils extend continuously from the uppermost portions of the cavity of the papilla to the mesenchyme of the condensing pre‐ossicular plate during stage 5. Degeneration is localized in a small area of the papilla during stages 3 and 4 but spreads throughout the mass during stage 5. Late in stage 5, necrotic epithelial cells are sloughed into the cavity of the papilla from its basal layer. These findings are discussed in relation to earlier light microscopic and experimental studies which have shown the papillae to be required for the subsequent development of the scleral ossicles in the subjacent mesenchyme.