tympanic antrum, a relatively large, irregular cavity in the superior anterior part of the mastoid process of the temporal bone, communicating with the mastoid air cells and lined by the extension of the mucous membrane of the tympanic cavity. The bony tegmen tympani separates the tympanic antrum from the middle fossa of the cranial cavity, and the lateral semicircular canal of the internal ear projects into the antrum. See also mastoid process.
