The cartilaginous portion is approximately 24 mm long and consists of a triangular plate of elastic fibrocartilage, the apex of which is attached to the margin of the medial end of the osseous portion of the tube, while its base lies directly under the mucous membrane of the nasopharynx, where it forms an elevation, the torus tubarius or cushion, behind the pharyngeal orifice of the tube. The edge of the osseous portion has a jagged margin that allows for the attachment of the cartilaginous portion. It may be considered part of the protympanum, starting below the tensor tympani muscle and gradually narrowing to end at the angle formed by the junction of squamous and petrous portions of the temporal bone. The bony (osseous) portion of the Eustachian tube has a length of approximately 12 mm. It consists of osseous and cartilaginous/fibrous tissue portions.
It is ~36 mm in length and is directed downward, forward, and medially, forming an angle of about 45 degrees with the sagittal plane and one of 30 to 40 degrees with the horizontal plane.
