ABSTRACT Cells of the dermal papilla influence the pattern of barb ridge formation during feather morphogenesis. The present ultrastructural study describes the fine structure of dermal cells and of dermal-epidermal contacts in forming feathers of different avian species. In the follicle, the collar epithelium is in contact with a dense dermis that becomes looser in the central part of the dermal papilla and gives rise to the pulp. Cells of the dermal papilla appear immature and unspecialized while those of the pulp are fibroblasts with short ergastoplasmic cisternae and produce sparse collagen fibrils. A direct apposition of mesenchymal elongation with epithelial cells of the collar is observed and the basement membrane is discontinuous in these areas. In the ramogenic collar, where barb ridges are formed and merge into a rachis, the basement membrane is more continuous and anchoring filaments are present. Small regions of the basement membrane are crossed by filopodia or by microvilli from mesenchymal cells and often contain pinocytotic vesicles. This suggests an exchange of molecules between dermal and epithelial cells that influence the morphogenesis of different feather types.
Buy this Article
|