Supportive fibrous tissues of the nasal epithelium with special reference to the site-dependent difference.

The nasal mucosa and submucosa likely contain both vascular beds against cold and dry air and resident immunoreactive cells against various antigens. Therefore, a specific fibrous structure seems to be necessary. Using histological specimens from 20 elderly cadavers, we examined the nasal mucosal and submucosal architecture. The ciliated columnar epithelium of the nasal mucosa was characterized by 1) a thick basal lamina, 2) few elastin-positive fibers beneath the epithelium, that was quite different from the nearby mucocutaneous junction area with a thick layer (0.3-0.8 mm) of elastic and oxytalan fibers corresponding to the skin dermis, 3) CD34-positive cells distributing diffusely in the submucosal tissue, and 4) few smooth muscle actin (SMA)-positive fibers beneath the epithelium. Some of submucosal fibrous structure appeared to express both elastin and CD34. CD34-positive arterioles were abundant beneath the ciliated epithelium, but they appeared negative for SMA antibody that cross-reacts with endothelium. Notably, the ciliated columnar epithelium was thin in the lateral wall of the nasal cavity, while the inferior concha carried the thick pseudostratified columnar epithelium. Strangely, the inferior or palatal wall of the nasal cavity was covered by the thick stratified epithelium. We found SMA-positive mucosal venous plexus in the lateral wall of nasal cavity, but the submucosa was filled with glands in the inferior concha. Vascular beds might be replaced by glands in the nasal submucosa. The site-dependent difference in the mucosal morphology as well as the absence of vascular beds might be a result of secondary change with aging.