The surface structure of the human nasal mucosa. I. Ciliated and metaplastic epithelium in normal individuals. A correlated study by scanning/transmission electron and light microscopy.

This study is part of a larger investigation, which includes morphometric and histopathologic studies, with the common objective of obtaining a comprehensive description of normal and altered nasal mucosa. Specimens from normal young subjects of both sexes (4 girls and 10 boys, 4-14 years of age) and middle-aged male persons (40-60 years of age) were investigated. Squamous metaplasia starts at an early age and becomes more prominent with increasing years. Pseudostratified epithelium is replaced by fully developed stratified squamous epithelium through a sequence of epithelial alterations starting with stratified cuboidal epithelium followed by mixed stratified cuboidal/stratified squamous epithelium. Each stage during this transformation can be readily recognized by its fine structural surface pattern. The changes in surface features during metaplastic transformation include (i) an increase in number and shortening of the microvilli, (ii) the appearance of microridges in squamous epithelium and (iii) alterations in mucus secretion, changing from macroapocrine in pseudostratified epithelium to microapocrine secretion in metaplasia. Metaplasia usually appeared in sharply demarcated areas, and each type is always surrounded by the directly preceding or succeeding variety of epithelium.