Histologic architecture of submucosal connective tissues in human eustachian tube with supplemental reference to the effects of aging.

Serial sections of 74 human eustachian tubes from 37 autopsy cases were examined microscopically to determine the histologic architecture of submucosal connective tissues. Abundant elastic fibers ran just beneath the mucosal epithelium of the eustachian tube. Two kinds of layers of collagenous fiber were observed an inner circular layer and an outer longitudinal layer. An "elastic fiber band" perfectly encircled the tubal lumen at the pharyngeal part of the eustachian tube. This band became less sharply defined at the osseous part. The two layers of collagenous fiber were contiguous, especially in the upper part of the tube, and ran from the pharyngeal orifice to the isthmus. Submucosal connective tissues were found to be undeveloped in fetal eustachian tubes. In children as well, elastic fibers were not fully developed, and circular banding of collagenous fibers was less marked. With advancing age, elastic fibers increased in number and became large and brittle. Both layers of collagenous fibers became thicker. The present data indicate that the submucosal connective tissues may play an important role in the elasticity of the eustachian tube itself and in the maintenance of the tubal framework. Gerontologic changes in the eustachian tube stroma have been considered pathophysiologically.