Assertion: nasopharynx's opening | /r/HasSubevent | the antrum
Facets:
Source sentences:
text: The back (posterior) wall partly separates the middle-ear cavity from another cavity, the mastoid antrum, but an opening in this wall leads to the antrum and to the small air cells of the mastoid process, which is the roughened, slightly bulging portion of the temporal bone just behind the external auditory canal and the auricle.