An ultrastructural study of the mucosal surface of the human inferior concha. I. Normal appearances.

A study is presented of normal human nasal mucosa. Tissue was taken from a defined site on the inferior concha to minimise individual variation and was studied using scanning and transmission electron microscopy. Three cell types were found at the epithelial surface; ciliated and non-ciliated columnar cells and goblet cells. The distribution of cell types varied greatly between specimens, perhaps owing to environmental factors. All cells bore microvilli which showed minor structural differences between the cell types. Two important features were common to all microvilli. Cytoplasmic filaments were seen running parallel to the long axis of the structure; these may be involved in microvillar motility. Also found was a prominent surface glycocalyx. This may help maintain the volume and viscosity of periciliary fluid; it may also prevent adhesion and tangling of microvilli and cilia. A notable feature of the cilia seen on transmission electron microscopy was the presence of occasional ciliary crowns; these claw-like projections from the cilial tips may be involved in the propulsion of mucus. The goblet cells showed apocrine secretory droplets which were extruded intact into the nasal lumen. This may help to preserve the integrity of the mucous and periciliary fluid layers. We conclude that the mechanism of mucus secretion and transport in the nose may involve several surface structures including ciliary crowns and microvilli. Their function is not yet clear and further study is indicated.