The role of the pars flaccida in the mechanics of the middle ear.

The role played by the pars flaccida in the functioning of the middle ear is not altogether clear. The aim of our research was to study the movements of pars flaccida in altering the air volume in the middle ear. By using a sond placed either in the tympanic bulla or in the Eustachian tube in the rat, the middle ear can be insufflated or aspirated with exact volumes of air. Pars flaccida reacted promptly to the changes, while pars tensa remained immobile. A large air volume caused perforation of the pars flaccida. It seems that pars flaccida's function may consist in maintaining a constant middle ear pressure within certain limits, by changing its position.