Lateral
On its lateral wall is the pharyngeal ostium of the Eustachian tube, somewhat triangular in shape, and bounded behind by a firm prominence, the torus tubarius or cushion, caused by the medial end of the cartilage of the tube which elevates the mucous membrane.
Two folds arise from the cartilaginous opening:
- vertical fold of mucous membrane, the salpingopharyngeal fold, stretches from the lower part of the torus; it contains the Salpingopharyngeus muscle.
- second and smaller fold, the salpingopalatine fold, stretches from the upper part of the torus to the palate; it contains the levator veli palatini muscle. The tensor veli palatini is lateral to the levator and does not contribute the fold, since the origin is deep to the cartilaginous opening.
Behind the ostium of the Eustachian tube is a deep recess, the pharyngeal recess (fossa of Rosenmüller).
Read more about this topic: Nasopharynx