The Eustachian tube is made up of

Eustachian tube Anatomy Eustachian tube, also called auditory or pharyngotympanic tube, connects nasopharynx with the tympanic cavity. In an adult, it is about 36 mm long and runs downwards, forwards and medially from its tympanic end, forming an angle of 45deg with the horizontal. It is divided into two pas: bony, which is posterolateral, forms one-third (12 mm) of the total length and fibrocailaginous, which is anteromedial, forms two-thirds (24 mm). The two pas meet at isthmus which is the narrowest pa of the tube. The fibrocailaginous pa of the tube is made of a single piece of cailage folded upon itself in such a way that it forms the whole of medial lamina, roof and a pa of the lateral lamina; the rest of its lateral Lamina is made of fibrous membrane. The tympanic end of the tube is bony, measures 5 x 2 mm and is situated in the anterior wall of middle ear, a little above the level of floor. The pharyngeal end of the tube is slit-like, veically. The cailage at this end raises an elevation called torus tubarius, which is situated in the lateral wall of the nasopharynx, 1-1.25 cm behind the posterior end of inferior turbinate. Ref : ENT textbook by Dhingra 6th edition Pgno : 57,58