Color enhanced scanning electron micrograph of the columnar epithelium of the human oviduct, at mid cycle. There are two types of cell present: ciliated and nonciliated (secretory). The latter produces a secretion which lubricates the environment and has a surface irregularly populated with tiny finger-like projections known as microvilli. The longer projections are cilia whose presence and length, as well as the activity of the secretory cells, are all under hormonal control.