Prenatal „Lumenization“ and Postnatal Pneumatization of theTympanic Cavity

Overview

The development of the tympanic cavity starts by the growth of the auditory tubeand its subsequent division into four sacs: saccus anticus, medius, superior and posticus. Thedevelopmental process of the cavity is a complex phenomenon, it involves gradual disappearanceof mesenchymal tissue, an increased volume of amniotic fluid, epithelization of the tympanic cavityand ossification of its walls. So far the mechanisms of disappearance of the mesenchyme were notelucidated. Although in the literature the term pneumatization of the tympanic cavity is used, wecannot agree with this term. Pneumatization should be associated with the presence of air in thecavity; the developing tympanic cavity is however before delivery filled with amniotic fluid. In theauthors’ opinion it is better to decribe this process during the period of intranterine developmentof the foetus by the term „lumenization“ as the lumen of the tympanic cavity is created which isfilled with amniotic fluid and not air.The process of prenatal lumenization depends on the presence of amniotic fluid, loss of mesenchymaltissue and the formation of the walls of the tympanic cavity which are at first made of cartilage andconnective tissue and gradually ossify. During postnatal development the amniotic fluid is replacedby air, which penetrates into the tympanic cavity via the auditory tube or by diffusion of blood gasesacross the wall of small capillaries in the mucoperiosteum of the tympanic cavity.

Key words:
tympanic cavity, embryonic development, lumenization, pneumatization,temporal bone