![]() The cartilaginous part of the Eustachian tube is about 24 mm in length and is formed of a triangular plate of elastic fibrocartilage, the apex of which is attached to the margin of the medial end of the bony part of the tube, while its base lies directly under the mucous membrane of the nasal part of the pharynx, where it forms an elevation, the torus tubarius or cushion, behind the pharyngeal opening of the auditory tube. The vestibule of the Eustachian tube is known as the protympanum, The protympanum is also known as the anterior part of the bony part of the tube. ![]() It begins in the anterior wall of the tympanic cavity, below the septum canalis musculotubarius, and, gradually narrowing, ends at the angle of junction of the squamous and the petrous parts of the temporal bone, its extremity presenting a jagged margin which serves for the attachment of the cartilaginous part. The bony part ( 1⁄ 3) nearest to the middle ear is made of bone and is about 12 mm in length. It consists of a bony part and a cartilaginous part. The Eustachian tube extends from the anterior wall of the middle ear to the lateral wall of the nasopharynx, approximately at the level of the inferior nasal concha. 3D reconstruction of the air cell system of the temporal bone including the eustachian tube and its narrowest area in close proximity to the ear, the isthmus ![]() Note the sac like shape of the structure. 3 D Reconstruction of the right Eustachian tube from Valsalva CT. What was thought of as the bony tube is really part of the air cell system of the temporal bone. Structure Upper respiratory system, showing entrance to auditory tube near middle The Eustachian tube has recently been redefined as the fibrocartilaginous structure connecting the air cell system of the temporal bone to the nose. A diver also experiences this change in pressure, but with greater rates of pressure change active opening of the Eustachian tube is required more frequently as the diver goes deeper, into higher pressure. Active opening of the Eustachian tube (through actions like swallowing or the Valsalva maneuver) is required to equalize the pressure between the middle ear and the ambient atmosphere as the plane descends. The air in the middle ear expands as the plane gains altitude, and pushes its way into the back of the nose and mouth on the way down, the volume of air in the middle ear shrinks, and a slight vacuum is produced. When taking off in an aircraft, the ambient air pressure goes from higher (on the ground) to lower (in the sky). Normally, the Eustachian tube is collapsed, but it gapes open with swallowing and with positive pressure, allowing the middle ear's pressure to adjust to the atmospheric pressure. Unlike the air of the ear canal, however, the air of the middle ear is not in direct contact with the atmosphere outside the body thus, a pressure difference can develop between the atmospheric pressure of the ear canal and the middle ear. In humans and other tetrapods, both the middle ear and the ear canal are normally filled with air. It is named after the sixteenth-century Italian anatomist Bartolomeo Eustachi. In adult humans, the Eustachian tube is approximately 35 mm (1.4 in) long and 3 mm (0.12 in) in diameter. In anatomy, the Eustachian tube ( / j uː ˈ s t eɪ ʃ ən/), also called the auditory tube or pharyngotympanic tube, is a tube that links the nasopharynx to the middle ear, of which it is also a part. ![]()
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