Abstract
There have been many studies concerning anatomical structures of the tympanic isthmus, but most of which were carried out by inspecting the tympanic isthmus superiorly from the attic after removing the tegmen tympani. Aims of the present study using human temporal bones were to examine the tympanic isthmus anteriorly, and to evaluate the pathway in the tympanum with reference to the mucosal folds in the middle ear.
The tympanic isthmus can be seen anteroposteriorly far behind the drum, located between the tensor tympani fold anteriorly and incudal fossa posteriorly, and in front of the facial canal. One of the components of the anterior tympanic isthmus, the tensor tympani fold, was thought to be playing an important role for directing the air flow into the tympanum, since the dye insuffiated from the ostium of the eustachian tube into the tympanic cavity, was deposited significantly both in the oval, and round window niche.
