The base of the cartilaginous portion of the eustachian tube that lies directly under the mucous membrane of the nasal part of the pharynx, forms an elevation or cushion, the torus tubarius or torus of the auditory tube, behind the pharyngeal orifice of the tube.
It has two folds:
Posteriorly the vertical fold of mucous membrane, the salpingopharyngeal fold, stretches from the lower part of the torus tubarius, it contains the Salpingopharyngeus muscle which originates from the superior border of the medial lamina of the cartilage of the auditory tube,and passes downward and blends with the posterior fasciculus of the palatopharyngeus muscle.
Anteriorly, the second and smaller fold, is the salpingopalatine fold, smaller than the salpingopharyngeal fold.
The salpingopalatine fold, contains some fibers of muscle, called salpingopalatine muscle, and it stretches from the superior border of lateral lamina of the cartilage, anteroinferiorly, to the back of the hard palate.