Postnatal changes in the connective tissue in the region lateral to the eustachian tube: possible relationship to tube function.

In order to delineate the possible role of connective tissue (CT) in the region lateral to the eustachian tube (ET) between the ET lumen and the tensor veli palatini muscle (TVPM), we studied the postnatal changes in the CT in histologic sections of human ET. In fetuses and neonates, the lateral region was filled with mesenchyme. Loose collagenous CT appeared first at 2 weeks of age, and in subjects older than 4 years of age, the collagen formed dense, meshlike structures attaching to both the subepithelial CT layer of the ET and the tendonlike membrane of the TVPM. Along the long axis of the ET, those attachments were distributed mainly in the region at the posterior part of the cartilaginous portion of the ET. Attachments to the subepithelial CT layer of the ET were distributed mainly in the upper half of the region. The dense, meshlike collagenous CT might help the ET to be opened by drawing the lateral wall of the ET lumen through inferolateral movement of the tendonlike membrane of the TVPM when the TVPM contracts. It may work to open mainly the parts that include the narrowest portion of the ET, and also the upper aspect of the ET lumen. Incomplete development of this structure in infants may be one of the factors associated with dysfunction in ET opening.