Ciliogenesis in the Mouse Oviduct

The mouse oviduct is a complex, coiled tube which can be conveniently divided into three distinct regions: fimbria, ampulla, and isthmus. The funnel-like fimbriated tip, through which the ovum is transported after ovulation, is the most heavily ciliated portion of the oviduct. In the adult the cilia function to transport ova into the ostium of the fimbriated tip, and from there into the ampullary region, where fertilization occurs (4). Interspersed among the ciliated ceils are a few nonciliated cells whose function appears to be secretory (15). During the development of the oviduct, ciliated cell differentiation is manifested by the production of large numbers of cilia on the surface of each cell. Although extensive formation of cilia on the mouse oviduct begins only after birth and continues for approximately 12 days, or until most of the cells of the epithelium are fully ciliated; a few ciliated cells are already present at birth. The formation of ciliated cells is random over the surface of the oviduct both in space and in time. However, cilia emerge in a somewhat ordered pattern on the surface of each individual cell. These results, obtained by scanning electron microscopy (SEM), add additional details to the description of the complex sequence of events which occur during ciliated cell differentiation and ciliary morphogenesis which could not have been predicted from previous studies by transmission electron microscopy (5, 6, 7, 13, 16, 21, 23). The limitations imposed by thin-sectioning techniques can be avoided in scanning electron microscopy, where large surface areas can be viewed simultaneously.