Intracytoplasmic lumina with and without cilia in both normal and pathologically altered nasal mucosa.

Two different types of intracytoplasmic lumina have been observed electron microscopically in pseudostratified and metaplastic human nasal mucosa: one type contains microvilli and the other contains both microvilli and cilia. The latter type was seen only in pseudostratified columnar epithelium, while the former was also observed in different stages of metaplasia. From these observations we conclude that the type of intracytoplasmic lumina is determined by the differential potential of the cells in which they occur. Serial sectioning demonstrated that these structures sometimes communicate with the extracellular space. The distinctly different ultrastructure of microvilli lining the intracytoplasmic lumina and the foldlike extensions of the cell membrane favors an intracellular genesis rather than a formation by invagination of the cell membrane. It is suggested that intracytoplasmic lumina occur as a consequence of dysregulation in the process of epithelial maturation.