On the lateral wall of the nasal part of the pharynx is the pharyngeal opening of auditory tube (pharyngeal ostium), somewhat triangular in shape, and bounded behind by a firm prominence, the torus or cushion, caused by the medial end of the cartilage of the tube which elevates the mucous membrane.
Czerwonka R, Złomaniec J, Semczuk B (1995). "[The endoscopic assessment of the pharyngeal opening of the auditory tube in recurrent exudative otitis media in children]". Otolaryngol Pol (in Polish) 49 (5): 426–30. PMID8714566.