Acid mucopolysaccharide layer of the surface nasal epithelium.

In the anterior tip of the inferior turbinate, the epithelium has microvilli which are covered by a mucopolysaccharide layer. This layer is about 0.8 mu in depth, well stained by ruthenium red and with a high density. The spaces between these microvilli are filled with this dense layer; therefore the movement of microvilli are suppressed, but this layer is a strong defensive line against ambient air. It is known that most inhaled particles are deposited in the anterior nares. So virus, microorganisms and antigens etc. will easily penetrate the epithelium if this layer becomes thin. Two centimeters behind the anterior tip where the epithelium is ciliated, the mucous layer over the cilia is less stained by ruthenium red and has a lower density than the anterior tip. This layer does not insert itself between the cilia. The fine filamentous mucopolysaccharide which seems flexible binds the cilias and the mucous layer. While the beat of cilia is not suppressed the inhaled particles cannot insert between cilia. In conclusion, the deep mucopolysaccharide layer over the anterior tip of the inferior turbinate and ciliary beat are important defensive mechanisms against the trauma of the ambient air.